1 /* 2 * Copyright (c) 2001, 2019, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #if !defined(__clang_major__) && defined(__GNUC__) 26 #define ATTRIBUTE_PRINTF(x,y) // FIXME, formats are a mess. 27 #endif 28 29 #include "precompiled.hpp" 30 #include "classfile/metadataOnStackMark.hpp" 31 #include "code/codeCache.hpp" 32 #include "code/icBuffer.hpp" 33 #include "gc_implementation/g1/bufferingOopClosure.hpp" 34 #include "gc_implementation/g1/concurrentG1Refine.hpp" 35 #include "gc_implementation/g1/concurrentG1RefineThread.hpp" 36 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp" 37 #include "gc_implementation/g1/g1AllocRegion.inline.hpp" 38 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp" 39 #include "gc_implementation/g1/g1CollectorPolicy.hpp" 40 #include "gc_implementation/g1/g1ErgoVerbose.hpp" 41 #include "gc_implementation/g1/g1EvacFailure.hpp" 42 #include "gc_implementation/g1/g1GCPhaseTimes.hpp" 43 #include "gc_implementation/g1/g1Log.hpp" 44 #include "gc_implementation/g1/g1MarkSweep.hpp" 45 #include "gc_implementation/g1/g1OopClosures.inline.hpp" 46 #include "gc_implementation/g1/g1ParScanThreadState.inline.hpp" 47 #include "gc_implementation/g1/g1RegionToSpaceMapper.hpp" 48 #include "gc_implementation/g1/g1RemSet.inline.hpp" 49 #include "gc_implementation/g1/g1RootProcessor.hpp" 50 #include "gc_implementation/g1/g1StringDedup.hpp" 51 #include "gc_implementation/g1/g1YCTypes.hpp" 52 #include "gc_implementation/g1/heapRegion.inline.hpp" 53 #include "gc_implementation/g1/heapRegionRemSet.hpp" 54 #include "gc_implementation/g1/heapRegionSet.inline.hpp" 55 #include "gc_implementation/g1/vm_operations_g1.hpp" 56 #include "gc_implementation/shared/gcHeapSummary.hpp" 57 #include "gc_implementation/shared/gcTimer.hpp" 58 #include "gc_implementation/shared/gcTrace.hpp" 59 #include "gc_implementation/shared/gcTraceTime.hpp" 60 #include "gc_implementation/shared/isGCActiveMark.hpp" 61 #include "memory/allocation.hpp" 62 #include "memory/gcLocker.inline.hpp" 63 #include "memory/generationSpec.hpp" 64 #include "memory/iterator.hpp" 65 #include "memory/referenceProcessor.hpp" 66 #include "oops/oop.inline.hpp" 67 #include "oops/oop.pcgc.inline.hpp" 68 #include "runtime/orderAccess.inline.hpp" 69 #include "runtime/vmThread.hpp" 70 71 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 72 73 // turn it on so that the contents of the young list (scan-only / 74 // to-be-collected) are printed at "strategic" points before / during 75 // / after the collection --- this is useful for debugging 76 #define YOUNG_LIST_VERBOSE 0 77 // CURRENT STATUS 78 // This file is under construction. Search for "FIXME". 79 80 // INVARIANTS/NOTES 81 // 82 // All allocation activity covered by the G1CollectedHeap interface is 83 // serialized by acquiring the HeapLock. This happens in mem_allocate 84 // and allocate_new_tlab, which are the "entry" points to the 85 // allocation code from the rest of the JVM. (Note that this does not 86 // apply to TLAB allocation, which is not part of this interface: it 87 // is done by clients of this interface.) 88 89 // Local to this file. 90 91 class RefineCardTableEntryClosure: public CardTableEntryClosure { 92 bool _concurrent; 93 public: 94 RefineCardTableEntryClosure() : _concurrent(true) { } 95 96 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 97 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false); 98 // This path is executed by the concurrent refine or mutator threads, 99 // concurrently, and so we do not care if card_ptr contains references 100 // that point into the collection set. 101 assert(!oops_into_cset, "should be"); 102 103 if (_concurrent && SuspendibleThreadSet::should_yield()) { 104 // Caller will actually yield. 105 return false; 106 } 107 // Otherwise, we finished successfully; return true. 108 return true; 109 } 110 111 void set_concurrent(bool b) { _concurrent = b; } 112 }; 113 114 115 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure { 116 size_t _num_processed; 117 CardTableModRefBS* _ctbs; 118 int _histo[256]; 119 120 public: 121 ClearLoggedCardTableEntryClosure() : 122 _num_processed(0), _ctbs(G1CollectedHeap::heap()->g1_barrier_set()) 123 { 124 for (int i = 0; i < 256; i++) _histo[i] = 0; 125 } 126 127 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 128 unsigned char* ujb = (unsigned char*)card_ptr; 129 int ind = (int)(*ujb); 130 _histo[ind]++; 131 132 *card_ptr = (jbyte)CardTableModRefBS::clean_card_val(); 133 _num_processed++; 134 135 return true; 136 } 137 138 size_t num_processed() { return _num_processed; } 139 140 void print_histo() { 141 gclog_or_tty->print_cr("Card table value histogram:"); 142 for (int i = 0; i < 256; i++) { 143 if (_histo[i] != 0) { 144 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]); 145 } 146 } 147 } 148 }; 149 150 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 151 private: 152 size_t _num_processed; 153 154 public: 155 RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { } 156 157 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 158 *card_ptr = CardTableModRefBS::dirty_card_val(); 159 _num_processed++; 160 return true; 161 } 162 163 size_t num_processed() const { return _num_processed; } 164 }; 165 166 YoungList::YoungList(G1CollectedHeap* g1h) : 167 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0), 168 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) { 169 guarantee(check_list_empty(false), "just making sure..."); 170 } 171 172 void YoungList::push_region(HeapRegion *hr) { 173 assert(!hr->is_young(), "should not already be young"); 174 assert(hr->get_next_young_region() == NULL, "cause it should!"); 175 176 hr->set_next_young_region(_head); 177 _head = hr; 178 179 _g1h->g1_policy()->set_region_eden(hr, (int) _length); 180 ++_length; 181 } 182 183 void YoungList::add_survivor_region(HeapRegion* hr) { 184 assert(hr->is_survivor(), "should be flagged as survivor region"); 185 assert(hr->get_next_young_region() == NULL, "cause it should!"); 186 187 hr->set_next_young_region(_survivor_head); 188 if (_survivor_head == NULL) { 189 _survivor_tail = hr; 190 } 191 _survivor_head = hr; 192 ++_survivor_length; 193 } 194 195 void YoungList::empty_list(HeapRegion* list) { 196 while (list != NULL) { 197 HeapRegion* next = list->get_next_young_region(); 198 list->set_next_young_region(NULL); 199 list->uninstall_surv_rate_group(); 200 // This is called before a Full GC and all the non-empty / 201 // non-humongous regions at the end of the Full GC will end up as 202 // old anyway. 203 list->set_old(); 204 list = next; 205 } 206 } 207 208 void YoungList::empty_list() { 209 assert(check_list_well_formed(), "young list should be well formed"); 210 211 empty_list(_head); 212 _head = NULL; 213 _length = 0; 214 215 empty_list(_survivor_head); 216 _survivor_head = NULL; 217 _survivor_tail = NULL; 218 _survivor_length = 0; 219 220 _last_sampled_rs_lengths = 0; 221 222 assert(check_list_empty(false), "just making sure..."); 223 } 224 225 bool YoungList::check_list_well_formed() { 226 bool ret = true; 227 228 uint length = 0; 229 HeapRegion* curr = _head; 230 HeapRegion* last = NULL; 231 while (curr != NULL) { 232 if (!curr->is_young()) { 233 gclog_or_tty->print_cr("### YOUNG REGION " PTR_FORMAT "-" PTR_FORMAT " " 234 "incorrectly tagged (y: %d, surv: %d)", 235 curr->bottom(), curr->end(), 236 curr->is_young(), curr->is_survivor()); 237 ret = false; 238 } 239 ++length; 240 last = curr; 241 curr = curr->get_next_young_region(); 242 } 243 ret = ret && (length == _length); 244 245 if (!ret) { 246 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!"); 247 gclog_or_tty->print_cr("### list has %u entries, _length is %u", 248 length, _length); 249 } 250 251 return ret; 252 } 253 254 bool YoungList::check_list_empty(bool check_sample) { 255 bool ret = true; 256 257 if (_length != 0) { 258 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u", 259 _length); 260 ret = false; 261 } 262 if (check_sample && _last_sampled_rs_lengths != 0) { 263 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths"); 264 ret = false; 265 } 266 if (_head != NULL) { 267 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head"); 268 ret = false; 269 } 270 if (!ret) { 271 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty"); 272 } 273 274 return ret; 275 } 276 277 void 278 YoungList::rs_length_sampling_init() { 279 _sampled_rs_lengths = 0; 280 _curr = _head; 281 } 282 283 bool 284 YoungList::rs_length_sampling_more() { 285 return _curr != NULL; 286 } 287 288 void 289 YoungList::rs_length_sampling_next() { 290 assert( _curr != NULL, "invariant" ); 291 size_t rs_length = _curr->rem_set()->occupied(); 292 293 _sampled_rs_lengths += rs_length; 294 295 // The current region may not yet have been added to the 296 // incremental collection set (it gets added when it is 297 // retired as the current allocation region). 298 if (_curr->in_collection_set()) { 299 // Update the collection set policy information for this region 300 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length); 301 } 302 303 _curr = _curr->get_next_young_region(); 304 if (_curr == NULL) { 305 _last_sampled_rs_lengths = _sampled_rs_lengths; 306 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths); 307 } 308 } 309 310 void 311 YoungList::reset_auxilary_lists() { 312 guarantee( is_empty(), "young list should be empty" ); 313 assert(check_list_well_formed(), "young list should be well formed"); 314 315 // Add survivor regions to SurvRateGroup. 316 _g1h->g1_policy()->note_start_adding_survivor_regions(); 317 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */); 318 319 int young_index_in_cset = 0; 320 for (HeapRegion* curr = _survivor_head; 321 curr != NULL; 322 curr = curr->get_next_young_region()) { 323 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset); 324 325 // The region is a non-empty survivor so let's add it to 326 // the incremental collection set for the next evacuation 327 // pause. 328 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr); 329 young_index_in_cset += 1; 330 } 331 assert((uint) young_index_in_cset == _survivor_length, "post-condition"); 332 _g1h->g1_policy()->note_stop_adding_survivor_regions(); 333 334 _head = _survivor_head; 335 _length = _survivor_length; 336 if (_survivor_head != NULL) { 337 assert(_survivor_tail != NULL, "cause it shouldn't be"); 338 assert(_survivor_length > 0, "invariant"); 339 _survivor_tail->set_next_young_region(NULL); 340 } 341 342 // Don't clear the survivor list handles until the start of 343 // the next evacuation pause - we need it in order to re-tag 344 // the survivor regions from this evacuation pause as 'young' 345 // at the start of the next. 346 347 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */); 348 349 assert(check_list_well_formed(), "young list should be well formed"); 350 } 351 352 void YoungList::print() { 353 HeapRegion* lists[] = {_head, _survivor_head}; 354 const char* names[] = {"YOUNG", "SURVIVOR"}; 355 356 for (uint list = 0; list < ARRAY_SIZE(lists); ++list) { 357 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]); 358 HeapRegion *curr = lists[list]; 359 if (curr == NULL) 360 gclog_or_tty->print_cr(" empty"); 361 while (curr != NULL) { 362 gclog_or_tty->print_cr(" " HR_FORMAT ", P: " PTR_FORMAT ", N: " PTR_FORMAT ", age: %4d", 363 HR_FORMAT_PARAMS(curr), 364 curr->prev_top_at_mark_start(), 365 curr->next_top_at_mark_start(), 366 curr->age_in_surv_rate_group_cond()); 367 curr = curr->get_next_young_region(); 368 } 369 } 370 371 gclog_or_tty->cr(); 372 } 373 374 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 375 OtherRegionsTable::invalidate(start_idx, num_regions); 376 } 377 378 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 379 // The from card cache is not the memory that is actually committed. So we cannot 380 // take advantage of the zero_filled parameter. 381 reset_from_card_cache(start_idx, num_regions); 382 } 383 384 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr) 385 { 386 // Claim the right to put the region on the dirty cards region list 387 // by installing a self pointer. 388 HeapRegion* next = hr->get_next_dirty_cards_region(); 389 if (next == NULL) { 390 HeapRegion* res = (HeapRegion*) 391 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(), 392 NULL); 393 if (res == NULL) { 394 HeapRegion* head; 395 do { 396 // Put the region to the dirty cards region list. 397 head = _dirty_cards_region_list; 398 next = (HeapRegion*) 399 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head); 400 if (next == head) { 401 assert(hr->get_next_dirty_cards_region() == hr, 402 "hr->get_next_dirty_cards_region() != hr"); 403 if (next == NULL) { 404 // The last region in the list points to itself. 405 hr->set_next_dirty_cards_region(hr); 406 } else { 407 hr->set_next_dirty_cards_region(next); 408 } 409 } 410 } while (next != head); 411 } 412 } 413 } 414 415 HeapRegion* G1CollectedHeap::pop_dirty_cards_region() 416 { 417 HeapRegion* head; 418 HeapRegion* hr; 419 do { 420 head = _dirty_cards_region_list; 421 if (head == NULL) { 422 return NULL; 423 } 424 HeapRegion* new_head = head->get_next_dirty_cards_region(); 425 if (head == new_head) { 426 // The last region. 427 new_head = NULL; 428 } 429 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list, 430 head); 431 } while (hr != head); 432 assert(hr != NULL, "invariant"); 433 hr->set_next_dirty_cards_region(NULL); 434 return hr; 435 } 436 437 #ifdef ASSERT 438 // A region is added to the collection set as it is retired 439 // so an address p can point to a region which will be in the 440 // collection set but has not yet been retired. This method 441 // therefore is only accurate during a GC pause after all 442 // regions have been retired. It is used for debugging 443 // to check if an nmethod has references to objects that can 444 // be move during a partial collection. Though it can be 445 // inaccurate, it is sufficient for G1 because the conservative 446 // implementation of is_scavengable() for G1 will indicate that 447 // all nmethods must be scanned during a partial collection. 448 bool G1CollectedHeap::is_in_partial_collection(const void* p) { 449 if (p == NULL) { 450 return false; 451 } 452 return heap_region_containing(p)->in_collection_set(); 453 } 454 #endif 455 456 // Returns true if the reference points to an object that 457 // can move in an incremental collection. 458 bool G1CollectedHeap::is_scavengable(const void* p) { 459 HeapRegion* hr = heap_region_containing(p); 460 return !hr->isHumongous(); 461 } 462 463 void G1CollectedHeap::check_ct_logs_at_safepoint() { 464 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 465 CardTableModRefBS* ct_bs = g1_barrier_set(); 466 467 // Count the dirty cards at the start. 468 CountNonCleanMemRegionClosure count1(this); 469 ct_bs->mod_card_iterate(&count1); 470 int orig_count = count1.n(); 471 472 // First clear the logged cards. 473 ClearLoggedCardTableEntryClosure clear; 474 dcqs.apply_closure_to_all_completed_buffers(&clear); 475 dcqs.iterate_closure_all_threads(&clear, false); 476 clear.print_histo(); 477 478 // Now ensure that there's no dirty cards. 479 CountNonCleanMemRegionClosure count2(this); 480 ct_bs->mod_card_iterate(&count2); 481 if (count2.n() != 0) { 482 gclog_or_tty->print_cr("Card table has %d entries; %d originally", 483 count2.n(), orig_count); 484 } 485 guarantee(count2.n() == 0, "Card table should be clean."); 486 487 RedirtyLoggedCardTableEntryClosure redirty; 488 dcqs.apply_closure_to_all_completed_buffers(&redirty); 489 dcqs.iterate_closure_all_threads(&redirty, false); 490 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.", 491 clear.num_processed(), orig_count); 492 guarantee(redirty.num_processed() == clear.num_processed(), 493 err_msg("Redirtied " SIZE_FORMAT " cards, bug cleared " SIZE_FORMAT, 494 redirty.num_processed(), clear.num_processed())); 495 496 CountNonCleanMemRegionClosure count3(this); 497 ct_bs->mod_card_iterate(&count3); 498 if (count3.n() != orig_count) { 499 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.", 500 orig_count, count3.n()); 501 guarantee(count3.n() >= orig_count, "Should have restored them all."); 502 } 503 } 504 505 // Private class members. 506 507 G1CollectedHeap* G1CollectedHeap::_g1h; 508 509 // Private methods. 510 511 HeapRegion* 512 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 513 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 514 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 515 if (!_secondary_free_list.is_empty()) { 516 if (G1ConcRegionFreeingVerbose) { 517 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 518 "secondary_free_list has %u entries", 519 _secondary_free_list.length()); 520 } 521 // It looks as if there are free regions available on the 522 // secondary_free_list. Let's move them to the free_list and try 523 // again to allocate from it. 524 append_secondary_free_list(); 525 526 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 527 "empty we should have moved at least one entry to the free_list"); 528 HeapRegion* res = _hrm.allocate_free_region(is_old); 529 if (G1ConcRegionFreeingVerbose) { 530 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 531 "allocated " HR_FORMAT " from secondary_free_list", 532 HR_FORMAT_PARAMS(res)); 533 } 534 return res; 535 } 536 537 // Wait here until we get notified either when (a) there are no 538 // more free regions coming or (b) some regions have been moved on 539 // the secondary_free_list. 540 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 541 } 542 543 if (G1ConcRegionFreeingVerbose) { 544 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 545 "could not allocate from secondary_free_list"); 546 } 547 return NULL; 548 } 549 550 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 551 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords, 552 "the only time we use this to allocate a humongous region is " 553 "when we are allocating a single humongous region"); 554 555 HeapRegion* res; 556 if (G1StressConcRegionFreeing) { 557 if (!_secondary_free_list.is_empty()) { 558 if (G1ConcRegionFreeingVerbose) { 559 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 560 "forced to look at the secondary_free_list"); 561 } 562 res = new_region_try_secondary_free_list(is_old); 563 if (res != NULL) { 564 return res; 565 } 566 } 567 } 568 569 res = _hrm.allocate_free_region(is_old); 570 571 if (res == NULL) { 572 if (G1ConcRegionFreeingVerbose) { 573 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 574 "res == NULL, trying the secondary_free_list"); 575 } 576 res = new_region_try_secondary_free_list(is_old); 577 } 578 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 579 // Currently, only attempts to allocate GC alloc regions set 580 // do_expand to true. So, we should only reach here during a 581 // safepoint. If this assumption changes we might have to 582 // reconsider the use of _expand_heap_after_alloc_failure. 583 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 584 585 ergo_verbose1(ErgoHeapSizing, 586 "attempt heap expansion", 587 ergo_format_reason("region allocation request failed") 588 ergo_format_byte("allocation request"), 589 word_size * HeapWordSize); 590 if (expand(word_size * HeapWordSize)) { 591 // Given that expand() succeeded in expanding the heap, and we 592 // always expand the heap by an amount aligned to the heap 593 // region size, the free list should in theory not be empty. 594 // In either case allocate_free_region() will check for NULL. 595 res = _hrm.allocate_free_region(is_old); 596 } else { 597 _expand_heap_after_alloc_failure = false; 598 } 599 } 600 return res; 601 } 602 603 HeapWord* 604 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 605 uint num_regions, 606 size_t word_size, 607 AllocationContext_t context) { 608 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 609 assert(isHumongous(word_size), "word_size should be humongous"); 610 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 611 612 // Index of last region in the series + 1. 613 uint last = first + num_regions; 614 615 // We need to initialize the region(s) we just discovered. This is 616 // a bit tricky given that it can happen concurrently with 617 // refinement threads refining cards on these regions and 618 // potentially wanting to refine the BOT as they are scanning 619 // those cards (this can happen shortly after a cleanup; see CR 620 // 6991377). So we have to set up the region(s) carefully and in 621 // a specific order. 622 623 // The word size sum of all the regions we will allocate. 624 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 625 assert(word_size <= word_size_sum, "sanity"); 626 627 // This will be the "starts humongous" region. 628 HeapRegion* first_hr = region_at(first); 629 // The header of the new object will be placed at the bottom of 630 // the first region. 631 HeapWord* new_obj = first_hr->bottom(); 632 // This will be the new end of the first region in the series that 633 // should also match the end of the last region in the series. 634 HeapWord* new_end = new_obj + word_size_sum; 635 // This will be the new top of the first region that will reflect 636 // this allocation. 637 HeapWord* new_top = new_obj + word_size; 638 639 // First, we need to zero the header of the space that we will be 640 // allocating. When we update top further down, some refinement 641 // threads might try to scan the region. By zeroing the header we 642 // ensure that any thread that will try to scan the region will 643 // come across the zero klass word and bail out. 644 // 645 // NOTE: It would not have been correct to have used 646 // CollectedHeap::fill_with_object() and make the space look like 647 // an int array. The thread that is doing the allocation will 648 // later update the object header to a potentially different array 649 // type and, for a very short period of time, the klass and length 650 // fields will be inconsistent. This could cause a refinement 651 // thread to calculate the object size incorrectly. 652 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 653 654 // We will set up the first region as "starts humongous". This 655 // will also update the BOT covering all the regions to reflect 656 // that there is a single object that starts at the bottom of the 657 // first region. 658 first_hr->set_startsHumongous(new_top, new_end); 659 first_hr->set_allocation_context(context); 660 // Then, if there are any, we will set up the "continues 661 // humongous" regions. 662 HeapRegion* hr = NULL; 663 for (uint i = first + 1; i < last; ++i) { 664 hr = region_at(i); 665 hr->set_continuesHumongous(first_hr); 666 hr->set_allocation_context(context); 667 } 668 // If we have "continues humongous" regions (hr != NULL), then the 669 // end of the last one should match new_end. 670 assert(hr == NULL || hr->end() == new_end, "sanity"); 671 672 // Up to this point no concurrent thread would have been able to 673 // do any scanning on any region in this series. All the top 674 // fields still point to bottom, so the intersection between 675 // [bottom,top] and [card_start,card_end] will be empty. Before we 676 // update the top fields, we'll do a storestore to make sure that 677 // no thread sees the update to top before the zeroing of the 678 // object header and the BOT initialization. 679 OrderAccess::storestore(); 680 681 // Now that the BOT and the object header have been initialized, 682 // we can update top of the "starts humongous" region. 683 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(), 684 "new_top should be in this region"); 685 first_hr->set_top(new_top); 686 if (_hr_printer.is_active()) { 687 HeapWord* bottom = first_hr->bottom(); 688 HeapWord* end = first_hr->orig_end(); 689 if ((first + 1) == last) { 690 // the series has a single humongous region 691 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top); 692 } else { 693 // the series has more than one humongous regions 694 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end); 695 } 696 } 697 698 // Now, we will update the top fields of the "continues humongous" 699 // regions. The reason we need to do this is that, otherwise, 700 // these regions would look empty and this will confuse parts of 701 // G1. For example, the code that looks for a consecutive number 702 // of empty regions will consider them empty and try to 703 // re-allocate them. We can extend is_empty() to also include 704 // !continuesHumongous(), but it is easier to just update the top 705 // fields here. The way we set top for all regions (i.e., top == 706 // end for all regions but the last one, top == new_top for the 707 // last one) is actually used when we will free up the humongous 708 // region in free_humongous_region(). 709 hr = NULL; 710 for (uint i = first + 1; i < last; ++i) { 711 hr = region_at(i); 712 if ((i + 1) == last) { 713 // last continues humongous region 714 assert(hr->bottom() < new_top && new_top <= hr->end(), 715 "new_top should fall on this region"); 716 hr->set_top(new_top); 717 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top); 718 } else { 719 // not last one 720 assert(new_top > hr->end(), "new_top should be above this region"); 721 hr->set_top(hr->end()); 722 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end()); 723 } 724 } 725 // If we have continues humongous regions (hr != NULL), then the 726 // end of the last one should match new_end and its top should 727 // match new_top. 728 assert(hr == NULL || 729 (hr->end() == new_end && hr->top() == new_top), "sanity"); 730 check_bitmaps("Humongous Region Allocation", first_hr); 731 732 assert(first_hr->used() == word_size * HeapWordSize, "invariant"); 733 _allocator->increase_used(first_hr->used()); 734 _humongous_set.add(first_hr); 735 736 return new_obj; 737 } 738 739 // If could fit into free regions w/o expansion, try. 740 // Otherwise, if can expand, do so. 741 // Otherwise, if using ex regions might help, try with ex given back. 742 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 743 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 744 745 verify_region_sets_optional(); 746 747 uint first = G1_NO_HRM_INDEX; 748 uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords); 749 750 if (obj_regions == 1) { 751 // Only one region to allocate, try to use a fast path by directly allocating 752 // from the free lists. Do not try to expand here, we will potentially do that 753 // later. 754 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 755 if (hr != NULL) { 756 first = hr->hrm_index(); 757 } 758 } else { 759 // We can't allocate humongous regions spanning more than one region while 760 // cleanupComplete() is running, since some of the regions we find to be 761 // empty might not yet be added to the free list. It is not straightforward 762 // to know in which list they are on so that we can remove them. We only 763 // need to do this if we need to allocate more than one region to satisfy the 764 // current humongous allocation request. If we are only allocating one region 765 // we use the one-region region allocation code (see above), that already 766 // potentially waits for regions from the secondary free list. 767 wait_while_free_regions_coming(); 768 append_secondary_free_list_if_not_empty_with_lock(); 769 770 // Policy: Try only empty regions (i.e. already committed first). Maybe we 771 // are lucky enough to find some. 772 first = _hrm.find_contiguous_only_empty(obj_regions); 773 if (first != G1_NO_HRM_INDEX) { 774 _hrm.allocate_free_regions_starting_at(first, obj_regions); 775 } 776 } 777 778 if (first == G1_NO_HRM_INDEX) { 779 // Policy: We could not find enough regions for the humongous object in the 780 // free list. Look through the heap to find a mix of free and uncommitted regions. 781 // If so, try expansion. 782 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 783 if (first != G1_NO_HRM_INDEX) { 784 // We found something. Make sure these regions are committed, i.e. expand 785 // the heap. Alternatively we could do a defragmentation GC. 786 ergo_verbose1(ErgoHeapSizing, 787 "attempt heap expansion", 788 ergo_format_reason("humongous allocation request failed") 789 ergo_format_byte("allocation request"), 790 word_size * HeapWordSize); 791 792 _hrm.expand_at(first, obj_regions); 793 g1_policy()->record_new_heap_size(num_regions()); 794 795 #ifdef ASSERT 796 for (uint i = first; i < first + obj_regions; ++i) { 797 HeapRegion* hr = region_at(i); 798 assert(hr->is_free(), "sanity"); 799 assert(hr->is_empty(), "sanity"); 800 assert(is_on_master_free_list(hr), "sanity"); 801 } 802 #endif 803 _hrm.allocate_free_regions_starting_at(first, obj_regions); 804 } else { 805 // Policy: Potentially trigger a defragmentation GC. 806 } 807 } 808 809 HeapWord* result = NULL; 810 if (first != G1_NO_HRM_INDEX) { 811 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 812 word_size, context); 813 assert(result != NULL, "it should always return a valid result"); 814 815 // A successful humongous object allocation changes the used space 816 // information of the old generation so we need to recalculate the 817 // sizes and update the jstat counters here. 818 g1mm()->update_sizes(); 819 } 820 821 verify_region_sets_optional(); 822 823 return result; 824 } 825 826 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 827 assert_heap_not_locked_and_not_at_safepoint(); 828 assert(!isHumongous(word_size), "we do not allow humongous TLABs"); 829 830 uint dummy_gc_count_before; 831 uint dummy_gclocker_retry_count = 0; 832 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 833 } 834 835 HeapWord* 836 G1CollectedHeap::mem_allocate(size_t word_size, 837 bool* gc_overhead_limit_was_exceeded) { 838 assert_heap_not_locked_and_not_at_safepoint(); 839 840 // Loop until the allocation is satisfied, or unsatisfied after GC. 841 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 842 uint gc_count_before; 843 844 HeapWord* result = NULL; 845 if (!isHumongous(word_size)) { 846 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 847 } else { 848 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 849 } 850 if (result != NULL) { 851 return result; 852 } 853 854 // Create the garbage collection operation... 855 VM_G1CollectForAllocation op(gc_count_before, word_size); 856 op.set_allocation_context(AllocationContext::current()); 857 858 // ...and get the VM thread to execute it. 859 VMThread::execute(&op); 860 861 if (op.prologue_succeeded() && op.pause_succeeded()) { 862 // If the operation was successful we'll return the result even 863 // if it is NULL. If the allocation attempt failed immediately 864 // after a Full GC, it's unlikely we'll be able to allocate now. 865 HeapWord* result = op.result(); 866 if (result != NULL && !isHumongous(word_size)) { 867 // Allocations that take place on VM operations do not do any 868 // card dirtying and we have to do it here. We only have to do 869 // this for non-humongous allocations, though. 870 dirty_young_block(result, word_size); 871 } 872 return result; 873 } else { 874 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 875 return NULL; 876 } 877 assert(op.result() == NULL, 878 "the result should be NULL if the VM op did not succeed"); 879 } 880 881 // Give a warning if we seem to be looping forever. 882 if ((QueuedAllocationWarningCount > 0) && 883 (try_count % QueuedAllocationWarningCount == 0)) { 884 warning("G1CollectedHeap::mem_allocate retries %d times", try_count); 885 } 886 } 887 888 ShouldNotReachHere(); 889 return NULL; 890 } 891 892 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 893 AllocationContext_t context, 894 uint* gc_count_before_ret, 895 uint* gclocker_retry_count_ret) { 896 // Make sure you read the note in attempt_allocation_humongous(). 897 898 assert_heap_not_locked_and_not_at_safepoint(); 899 assert(!isHumongous(word_size), "attempt_allocation_slow() should not " 900 "be called for humongous allocation requests"); 901 902 // We should only get here after the first-level allocation attempt 903 // (attempt_allocation()) failed to allocate. 904 905 // We will loop until a) we manage to successfully perform the 906 // allocation or b) we successfully schedule a collection which 907 // fails to perform the allocation. b) is the only case when we'll 908 // return NULL. 909 HeapWord* result = NULL; 910 for (int try_count = 1; /* we'll return */; try_count += 1) { 911 bool should_try_gc; 912 uint gc_count_before; 913 914 { 915 MutexLockerEx x(Heap_lock); 916 result = _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size, 917 false /* bot_updates */); 918 if (result != NULL) { 919 return result; 920 } 921 922 // If we reach here, attempt_allocation_locked() above failed to 923 // allocate a new region. So the mutator alloc region should be NULL. 924 assert(_allocator->mutator_alloc_region(context)->get() == NULL, "only way to get here"); 925 926 if (GC_locker::is_active_and_needs_gc()) { 927 if (g1_policy()->can_expand_young_list()) { 928 // No need for an ergo verbose message here, 929 // can_expand_young_list() does this when it returns true. 930 result = _allocator->mutator_alloc_region(context)->attempt_allocation_force(word_size, 931 false /* bot_updates */); 932 if (result != NULL) { 933 return result; 934 } 935 } 936 should_try_gc = false; 937 } else { 938 // The GCLocker may not be active but the GCLocker initiated 939 // GC may not yet have been performed (GCLocker::needs_gc() 940 // returns true). In this case we do not try this GC and 941 // wait until the GCLocker initiated GC is performed, and 942 // then retry the allocation. 943 if (GC_locker::needs_gc()) { 944 should_try_gc = false; 945 } else { 946 // Read the GC count while still holding the Heap_lock. 947 gc_count_before = total_collections(); 948 should_try_gc = true; 949 } 950 } 951 } 952 953 if (should_try_gc) { 954 bool succeeded; 955 result = do_collection_pause(word_size, gc_count_before, &succeeded, 956 GCCause::_g1_inc_collection_pause); 957 if (result != NULL) { 958 assert(succeeded, "only way to get back a non-NULL result"); 959 return result; 960 } 961 962 if (succeeded) { 963 // If we get here we successfully scheduled a collection which 964 // failed to allocate. No point in trying to allocate 965 // further. We'll just return NULL. 966 MutexLockerEx x(Heap_lock); 967 *gc_count_before_ret = total_collections(); 968 return NULL; 969 } 970 } else { 971 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 972 MutexLockerEx x(Heap_lock); 973 *gc_count_before_ret = total_collections(); 974 return NULL; 975 } 976 // The GCLocker is either active or the GCLocker initiated 977 // GC has not yet been performed. Stall until it is and 978 // then retry the allocation. 979 GC_locker::stall_until_clear(); 980 (*gclocker_retry_count_ret) += 1; 981 } 982 983 // We can reach here if we were unsuccessful in scheduling a 984 // collection (because another thread beat us to it) or if we were 985 // stalled due to the GC locker. In either can we should retry the 986 // allocation attempt in case another thread successfully 987 // performed a collection and reclaimed enough space. We do the 988 // first attempt (without holding the Heap_lock) here and the 989 // follow-on attempt will be at the start of the next loop 990 // iteration (after taking the Heap_lock). 991 result = _allocator->mutator_alloc_region(context)->attempt_allocation(word_size, 992 false /* bot_updates */); 993 if (result != NULL) { 994 return result; 995 } 996 997 // Give a warning if we seem to be looping forever. 998 if ((QueuedAllocationWarningCount > 0) && 999 (try_count % QueuedAllocationWarningCount == 0)) { 1000 warning("G1CollectedHeap::attempt_allocation_slow() " 1001 "retries %d times", try_count); 1002 } 1003 } 1004 1005 ShouldNotReachHere(); 1006 return NULL; 1007 } 1008 1009 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 1010 uint* gc_count_before_ret, 1011 uint* gclocker_retry_count_ret) { 1012 // The structure of this method has a lot of similarities to 1013 // attempt_allocation_slow(). The reason these two were not merged 1014 // into a single one is that such a method would require several "if 1015 // allocation is not humongous do this, otherwise do that" 1016 // conditional paths which would obscure its flow. In fact, an early 1017 // version of this code did use a unified method which was harder to 1018 // follow and, as a result, it had subtle bugs that were hard to 1019 // track down. So keeping these two methods separate allows each to 1020 // be more readable. It will be good to keep these two in sync as 1021 // much as possible. 1022 1023 assert_heap_not_locked_and_not_at_safepoint(); 1024 assert(isHumongous(word_size), "attempt_allocation_humongous() " 1025 "should only be called for humongous allocations"); 1026 1027 // Humongous objects can exhaust the heap quickly, so we should check if we 1028 // need to start a marking cycle at each humongous object allocation. We do 1029 // the check before we do the actual allocation. The reason for doing it 1030 // before the allocation is that we avoid having to keep track of the newly 1031 // allocated memory while we do a GC. 1032 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 1033 word_size)) { 1034 collect(GCCause::_g1_humongous_allocation); 1035 } 1036 1037 // We will loop until a) we manage to successfully perform the 1038 // allocation or b) we successfully schedule a collection which 1039 // fails to perform the allocation. b) is the only case when we'll 1040 // return NULL. 1041 HeapWord* result = NULL; 1042 for (int try_count = 1; /* we'll return */; try_count += 1) { 1043 bool should_try_gc; 1044 uint gc_count_before; 1045 1046 { 1047 MutexLockerEx x(Heap_lock); 1048 1049 // Given that humongous objects are not allocated in young 1050 // regions, we'll first try to do the allocation without doing a 1051 // collection hoping that there's enough space in the heap. 1052 result = humongous_obj_allocate(word_size, AllocationContext::current()); 1053 if (result != NULL) { 1054 return result; 1055 } 1056 1057 if (GC_locker::is_active_and_needs_gc()) { 1058 should_try_gc = false; 1059 } else { 1060 // The GCLocker may not be active but the GCLocker initiated 1061 // GC may not yet have been performed (GCLocker::needs_gc() 1062 // returns true). In this case we do not try this GC and 1063 // wait until the GCLocker initiated GC is performed, and 1064 // then retry the allocation. 1065 if (GC_locker::needs_gc()) { 1066 should_try_gc = false; 1067 } else { 1068 // Read the GC count while still holding the Heap_lock. 1069 gc_count_before = total_collections(); 1070 should_try_gc = true; 1071 } 1072 } 1073 } 1074 1075 if (should_try_gc) { 1076 // If we failed to allocate the humongous object, we should try to 1077 // do a collection pause (if we're allowed) in case it reclaims 1078 // enough space for the allocation to succeed after the pause. 1079 1080 bool succeeded; 1081 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1082 GCCause::_g1_humongous_allocation); 1083 if (result != NULL) { 1084 assert(succeeded, "only way to get back a non-NULL result"); 1085 return result; 1086 } 1087 1088 if (succeeded) { 1089 // If we get here we successfully scheduled a collection which 1090 // failed to allocate. No point in trying to allocate 1091 // further. We'll just return NULL. 1092 MutexLockerEx x(Heap_lock); 1093 *gc_count_before_ret = total_collections(); 1094 return NULL; 1095 } 1096 } else { 1097 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1098 MutexLockerEx x(Heap_lock); 1099 *gc_count_before_ret = total_collections(); 1100 return NULL; 1101 } 1102 // The GCLocker is either active or the GCLocker initiated 1103 // GC has not yet been performed. Stall until it is and 1104 // then retry the allocation. 1105 GC_locker::stall_until_clear(); 1106 (*gclocker_retry_count_ret) += 1; 1107 } 1108 1109 // We can reach here if we were unsuccessful in scheduling a 1110 // collection (because another thread beat us to it) or if we were 1111 // stalled due to the GC locker. In either can we should retry the 1112 // allocation attempt in case another thread successfully 1113 // performed a collection and reclaimed enough space. Give a 1114 // warning if we seem to be looping forever. 1115 1116 if ((QueuedAllocationWarningCount > 0) && 1117 (try_count % QueuedAllocationWarningCount == 0)) { 1118 warning("G1CollectedHeap::attempt_allocation_humongous() " 1119 "retries %d times", try_count); 1120 } 1121 } 1122 1123 ShouldNotReachHere(); 1124 return NULL; 1125 } 1126 1127 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1128 AllocationContext_t context, 1129 bool expect_null_mutator_alloc_region) { 1130 assert_at_safepoint(true /* should_be_vm_thread */); 1131 assert(_allocator->mutator_alloc_region(context)->get() == NULL || 1132 !expect_null_mutator_alloc_region, 1133 "the current alloc region was unexpectedly found to be non-NULL"); 1134 1135 if (!isHumongous(word_size)) { 1136 return _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size, 1137 false /* bot_updates */); 1138 } else { 1139 HeapWord* result = humongous_obj_allocate(word_size, context); 1140 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1141 g1_policy()->set_initiate_conc_mark_if_possible(); 1142 } 1143 return result; 1144 } 1145 1146 ShouldNotReachHere(); 1147 } 1148 1149 class PostMCRemSetClearClosure: public HeapRegionClosure { 1150 G1CollectedHeap* _g1h; 1151 ModRefBarrierSet* _mr_bs; 1152 public: 1153 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) : 1154 _g1h(g1h), _mr_bs(mr_bs) {} 1155 1156 bool doHeapRegion(HeapRegion* r) { 1157 HeapRegionRemSet* hrrs = r->rem_set(); 1158 1159 if (r->continuesHumongous()) { 1160 // We'll assert that the strong code root list and RSet is empty 1161 assert(hrrs->strong_code_roots_list_length() == 0, "sanity"); 1162 assert(hrrs->occupied() == 0, "RSet should be empty"); 1163 return false; 1164 } 1165 1166 _g1h->reset_gc_time_stamps(r); 1167 hrrs->clear(); 1168 // You might think here that we could clear just the cards 1169 // corresponding to the used region. But no: if we leave a dirty card 1170 // in a region we might allocate into, then it would prevent that card 1171 // from being enqueued, and cause it to be missed. 1172 // Re: the performance cost: we shouldn't be doing full GC anyway! 1173 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1174 1175 return false; 1176 } 1177 }; 1178 1179 void G1CollectedHeap::clear_rsets_post_compaction() { 1180 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set()); 1181 heap_region_iterate(&rs_clear); 1182 } 1183 1184 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1185 G1CollectedHeap* _g1h; 1186 UpdateRSOopClosure _cl; 1187 int _worker_i; 1188 public: 1189 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) : 1190 _cl(g1->g1_rem_set(), worker_i), 1191 _worker_i(worker_i), 1192 _g1h(g1) 1193 { } 1194 1195 bool doHeapRegion(HeapRegion* r) { 1196 if (!r->continuesHumongous()) { 1197 _cl.set_from(r); 1198 r->oop_iterate(&_cl); 1199 } 1200 return false; 1201 } 1202 }; 1203 1204 class ParRebuildRSTask: public AbstractGangTask { 1205 G1CollectedHeap* _g1; 1206 public: 1207 ParRebuildRSTask(G1CollectedHeap* g1) 1208 : AbstractGangTask("ParRebuildRSTask"), 1209 _g1(g1) 1210 { } 1211 1212 void work(uint worker_id) { 1213 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id); 1214 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id, 1215 _g1->workers()->active_workers(), 1216 HeapRegion::RebuildRSClaimValue); 1217 } 1218 }; 1219 1220 class PostCompactionPrinterClosure: public HeapRegionClosure { 1221 private: 1222 G1HRPrinter* _hr_printer; 1223 public: 1224 bool doHeapRegion(HeapRegion* hr) { 1225 assert(!hr->is_young(), "not expecting to find young regions"); 1226 if (hr->is_free()) { 1227 // We only generate output for non-empty regions. 1228 } else if (hr->startsHumongous()) { 1229 if (hr->region_num() == 1) { 1230 // single humongous region 1231 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous); 1232 } else { 1233 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous); 1234 } 1235 } else if (hr->continuesHumongous()) { 1236 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous); 1237 } else if (hr->is_old()) { 1238 _hr_printer->post_compaction(hr, G1HRPrinter::Old); 1239 } else { 1240 ShouldNotReachHere(); 1241 } 1242 return false; 1243 } 1244 1245 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1246 : _hr_printer(hr_printer) { } 1247 }; 1248 1249 void G1CollectedHeap::print_hrm_post_compaction() { 1250 PostCompactionPrinterClosure cl(hr_printer()); 1251 heap_region_iterate(&cl); 1252 } 1253 1254 bool G1CollectedHeap::do_collection(bool explicit_gc, 1255 bool clear_all_soft_refs, 1256 size_t word_size) { 1257 assert_at_safepoint(true /* should_be_vm_thread */); 1258 1259 if (GC_locker::check_active_before_gc()) { 1260 return false; 1261 } 1262 1263 STWGCTimer* gc_timer = G1MarkSweep::gc_timer(); 1264 gc_timer->register_gc_start(); 1265 1266 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer(); 1267 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start()); 1268 1269 SvcGCMarker sgcm(SvcGCMarker::FULL); 1270 ResourceMark rm; 1271 1272 print_heap_before_gc(); 1273 trace_heap_before_gc(gc_tracer); 1274 1275 size_t metadata_prev_used = MetaspaceAux::used_bytes(); 1276 1277 verify_region_sets_optional(); 1278 1279 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1280 collector_policy()->should_clear_all_soft_refs(); 1281 1282 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1283 1284 { 1285 IsGCActiveMark x; 1286 1287 // Timing 1288 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant"); 1289 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 1290 1291 { 1292 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id()); 1293 TraceCollectorStats tcs(g1mm()->full_collection_counters()); 1294 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); 1295 1296 double start = os::elapsedTime(); 1297 g1_policy()->record_full_collection_start(); 1298 1299 // Note: When we have a more flexible GC logging framework that 1300 // allows us to add optional attributes to a GC log record we 1301 // could consider timing and reporting how long we wait in the 1302 // following two methods. 1303 wait_while_free_regions_coming(); 1304 // If we start the compaction before the CM threads finish 1305 // scanning the root regions we might trip them over as we'll 1306 // be moving objects / updating references. So let's wait until 1307 // they are done. By telling them to abort, they should complete 1308 // early. 1309 _cm->root_regions()->abort(); 1310 _cm->root_regions()->wait_until_scan_finished(); 1311 append_secondary_free_list_if_not_empty_with_lock(); 1312 1313 gc_prologue(true); 1314 increment_total_collections(true /* full gc */); 1315 increment_old_marking_cycles_started(); 1316 1317 assert(used() == recalculate_used(), "Should be equal"); 1318 1319 verify_before_gc(); 1320 1321 check_bitmaps("Full GC Start"); 1322 pre_full_gc_dump(gc_timer); 1323 1324 COMPILER2_PRESENT(DerivedPointerTable::clear()); 1325 1326 // Disable discovery and empty the discovered lists 1327 // for the CM ref processor. 1328 ref_processor_cm()->disable_discovery(); 1329 ref_processor_cm()->abandon_partial_discovery(); 1330 ref_processor_cm()->verify_no_references_recorded(); 1331 1332 // Abandon current iterations of concurrent marking and concurrent 1333 // refinement, if any are in progress. We have to do this before 1334 // wait_until_scan_finished() below. 1335 concurrent_mark()->abort(); 1336 1337 // Make sure we'll choose a new allocation region afterwards. 1338 _allocator->release_mutator_alloc_region(); 1339 _allocator->abandon_gc_alloc_regions(); 1340 g1_rem_set()->cleanupHRRS(); 1341 1342 // We should call this after we retire any currently active alloc 1343 // regions so that all the ALLOC / RETIRE events are generated 1344 // before the start GC event. 1345 _hr_printer.start_gc(true /* full */, (size_t) total_collections()); 1346 1347 // We may have added regions to the current incremental collection 1348 // set between the last GC or pause and now. We need to clear the 1349 // incremental collection set and then start rebuilding it afresh 1350 // after this full GC. 1351 abandon_collection_set(g1_policy()->inc_cset_head()); 1352 g1_policy()->clear_incremental_cset(); 1353 g1_policy()->stop_incremental_cset_building(); 1354 1355 tear_down_region_sets(false /* free_list_only */); 1356 g1_policy()->set_gcs_are_young(true); 1357 1358 // See the comments in g1CollectedHeap.hpp and 1359 // G1CollectedHeap::ref_processing_init() about 1360 // how reference processing currently works in G1. 1361 1362 // Temporarily make discovery by the STW ref processor single threaded (non-MT). 1363 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false); 1364 1365 // Temporarily clear the STW ref processor's _is_alive_non_header field. 1366 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL); 1367 1368 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/); 1369 ref_processor_stw()->setup_policy(do_clear_all_soft_refs); 1370 1371 // Do collection work 1372 { 1373 HandleMark hm; // Discard invalid handles created during gc 1374 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs); 1375 } 1376 1377 assert(num_free_regions() == 0, "we should not have added any free regions"); 1378 rebuild_region_sets(false /* free_list_only */); 1379 1380 // Enqueue any discovered reference objects that have 1381 // not been removed from the discovered lists. 1382 ref_processor_stw()->enqueue_discovered_references(); 1383 1384 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 1385 1386 MemoryService::track_memory_usage(); 1387 1388 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1389 ref_processor_stw()->verify_no_references_recorded(); 1390 1391 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1392 ClassLoaderDataGraph::purge(); 1393 MetaspaceAux::verify_metrics(); 1394 1395 // Note: since we've just done a full GC, concurrent 1396 // marking is no longer active. Therefore we need not 1397 // re-enable reference discovery for the CM ref processor. 1398 // That will be done at the start of the next marking cycle. 1399 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1400 ref_processor_cm()->verify_no_references_recorded(); 1401 1402 reset_gc_time_stamp(); 1403 // Since everything potentially moved, we will clear all remembered 1404 // sets, and clear all cards. Later we will rebuild remembered 1405 // sets. We will also reset the GC time stamps of the regions. 1406 clear_rsets_post_compaction(); 1407 check_gc_time_stamps(); 1408 1409 // Resize the heap if necessary. 1410 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size); 1411 1412 if (_hr_printer.is_active()) { 1413 // We should do this after we potentially resize the heap so 1414 // that all the COMMIT / UNCOMMIT events are generated before 1415 // the end GC event. 1416 1417 print_hrm_post_compaction(); 1418 _hr_printer.end_gc(true /* full */, (size_t) total_collections()); 1419 } 1420 1421 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 1422 if (hot_card_cache->use_cache()) { 1423 hot_card_cache->reset_card_counts(); 1424 hot_card_cache->reset_hot_cache(); 1425 } 1426 1427 // Rebuild remembered sets of all regions. 1428 if (G1CollectedHeap::use_parallel_gc_threads()) { 1429 uint n_workers = 1430 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 1431 workers()->active_workers(), 1432 Threads::number_of_non_daemon_threads()); 1433 assert(UseDynamicNumberOfGCThreads || 1434 n_workers == workers()->total_workers(), 1435 "If not dynamic should be using all the workers"); 1436 workers()->set_active_workers(n_workers); 1437 // Set parallel threads in the heap (_n_par_threads) only 1438 // before a parallel phase and always reset it to 0 after 1439 // the phase so that the number of parallel threads does 1440 // no get carried forward to a serial phase where there 1441 // may be code that is "possibly_parallel". 1442 set_par_threads(n_workers); 1443 1444 ParRebuildRSTask rebuild_rs_task(this); 1445 assert(check_heap_region_claim_values( 1446 HeapRegion::InitialClaimValue), "sanity check"); 1447 assert(UseDynamicNumberOfGCThreads || 1448 workers()->active_workers() == workers()->total_workers(), 1449 "Unless dynamic should use total workers"); 1450 // Use the most recent number of active workers 1451 assert(workers()->active_workers() > 0, 1452 "Active workers not properly set"); 1453 set_par_threads(workers()->active_workers()); 1454 workers()->run_task(&rebuild_rs_task); 1455 set_par_threads(0); 1456 assert(check_heap_region_claim_values( 1457 HeapRegion::RebuildRSClaimValue), "sanity check"); 1458 reset_heap_region_claim_values(); 1459 } else { 1460 RebuildRSOutOfRegionClosure rebuild_rs(this); 1461 heap_region_iterate(&rebuild_rs); 1462 } 1463 1464 // Rebuild the strong code root lists for each region 1465 rebuild_strong_code_roots(); 1466 1467 // Purge code root memory 1468 purge_code_root_memory(); 1469 1470 if (true) { // FIXME 1471 MetaspaceGC::compute_new_size(); 1472 } 1473 1474 #ifdef TRACESPINNING 1475 ParallelTaskTerminator::print_termination_counts(); 1476 #endif 1477 1478 // Discard all rset updates 1479 JavaThread::dirty_card_queue_set().abandon_logs(); 1480 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1481 1482 _young_list->reset_sampled_info(); 1483 // At this point there should be no regions in the 1484 // entire heap tagged as young. 1485 assert(check_young_list_empty(true /* check_heap */), 1486 "young list should be empty at this point"); 1487 1488 // Update the number of full collections that have been completed. 1489 increment_old_marking_cycles_completed(false /* concurrent */); 1490 1491 _hrm.verify_optional(); 1492 verify_region_sets_optional(); 1493 1494 verify_after_gc(); 1495 1496 // Clear the previous marking bitmap, if needed for bitmap verification. 1497 // Note we cannot do this when we clear the next marking bitmap in 1498 // ConcurrentMark::abort() above since VerifyDuringGC verifies the 1499 // objects marked during a full GC against the previous bitmap. 1500 // But we need to clear it before calling check_bitmaps below since 1501 // the full GC has compacted objects and updated TAMS but not updated 1502 // the prev bitmap. 1503 if (G1VerifyBitmaps) { 1504 ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll(); 1505 } 1506 check_bitmaps("Full GC End"); 1507 1508 // Start a new incremental collection set for the next pause 1509 assert(g1_policy()->collection_set() == NULL, "must be"); 1510 g1_policy()->start_incremental_cset_building(); 1511 1512 clear_cset_fast_test(); 1513 1514 _allocator->init_mutator_alloc_region(); 1515 1516 double end = os::elapsedTime(); 1517 g1_policy()->record_full_collection_end(); 1518 1519 if (G1Log::fine()) { 1520 g1_policy()->print_heap_transition(); 1521 } 1522 1523 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 1524 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 1525 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 1526 // before any GC notifications are raised. 1527 g1mm()->update_sizes(); 1528 1529 gc_epilogue(true); 1530 } 1531 1532 if (G1Log::finer()) { 1533 g1_policy()->print_detailed_heap_transition(true /* full */); 1534 } 1535 1536 print_heap_after_gc(); 1537 trace_heap_after_gc(gc_tracer); 1538 1539 post_full_gc_dump(gc_timer); 1540 1541 gc_timer->register_gc_end(); 1542 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions()); 1543 } 1544 1545 return true; 1546 } 1547 1548 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1549 // do_collection() will return whether it succeeded in performing 1550 // the GC. Currently, there is no facility on the 1551 // do_full_collection() API to notify the caller than the collection 1552 // did not succeed (e.g., because it was locked out by the GC 1553 // locker). So, right now, we'll ignore the return value. 1554 bool dummy = do_collection(true, /* explicit_gc */ 1555 clear_all_soft_refs, 1556 0 /* word_size */); 1557 } 1558 1559 // This code is mostly copied from TenuredGeneration. 1560 void 1561 G1CollectedHeap:: 1562 resize_if_necessary_after_full_collection(size_t word_size) { 1563 // Include the current allocation, if any, and bytes that will be 1564 // pre-allocated to support collections, as "used". 1565 const size_t used_after_gc = used(); 1566 const size_t capacity_after_gc = capacity(); 1567 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1568 1569 // This is enforced in arguments.cpp. 1570 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1571 "otherwise the code below doesn't make sense"); 1572 1573 // We don't have floating point command-line arguments 1574 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1575 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1576 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1577 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1578 1579 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1580 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1581 1582 // We have to be careful here as these two calculations can overflow 1583 // 32-bit size_t's. 1584 double used_after_gc_d = (double) used_after_gc; 1585 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1586 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1587 1588 // Let's make sure that they are both under the max heap size, which 1589 // by default will make them fit into a size_t. 1590 double desired_capacity_upper_bound = (double) max_heap_size; 1591 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1592 desired_capacity_upper_bound); 1593 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1594 desired_capacity_upper_bound); 1595 1596 // We can now safely turn them into size_t's. 1597 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1598 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1599 1600 // This assert only makes sense here, before we adjust them 1601 // with respect to the min and max heap size. 1602 assert(minimum_desired_capacity <= maximum_desired_capacity, 1603 err_msg("minimum_desired_capacity = " SIZE_FORMAT ", " 1604 "maximum_desired_capacity = " SIZE_FORMAT, 1605 minimum_desired_capacity, maximum_desired_capacity)); 1606 1607 // Should not be greater than the heap max size. No need to adjust 1608 // it with respect to the heap min size as it's a lower bound (i.e., 1609 // we'll try to make the capacity larger than it, not smaller). 1610 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1611 // Should not be less than the heap min size. No need to adjust it 1612 // with respect to the heap max size as it's an upper bound (i.e., 1613 // we'll try to make the capacity smaller than it, not greater). 1614 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1615 1616 if (capacity_after_gc < minimum_desired_capacity) { 1617 // Don't expand unless it's significant 1618 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1619 ergo_verbose4(ErgoHeapSizing, 1620 "attempt heap expansion", 1621 ergo_format_reason("capacity lower than " 1622 "min desired capacity after Full GC") 1623 ergo_format_byte("capacity") 1624 ergo_format_byte("occupancy") 1625 ergo_format_byte_perc("min desired capacity"), 1626 capacity_after_gc, used_after_gc, 1627 minimum_desired_capacity, (double) MinHeapFreeRatio); 1628 expand(expand_bytes); 1629 1630 // No expansion, now see if we want to shrink 1631 } else if (capacity_after_gc > maximum_desired_capacity) { 1632 // Capacity too large, compute shrinking size 1633 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1634 ergo_verbose4(ErgoHeapSizing, 1635 "attempt heap shrinking", 1636 ergo_format_reason("capacity higher than " 1637 "max desired capacity after Full GC") 1638 ergo_format_byte("capacity") 1639 ergo_format_byte("occupancy") 1640 ergo_format_byte_perc("max desired capacity"), 1641 capacity_after_gc, used_after_gc, 1642 maximum_desired_capacity, (double) MaxHeapFreeRatio); 1643 shrink(shrink_bytes); 1644 } 1645 } 1646 1647 1648 HeapWord* 1649 G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1650 AllocationContext_t context, 1651 bool* succeeded) { 1652 assert_at_safepoint(true /* should_be_vm_thread */); 1653 1654 *succeeded = true; 1655 // Let's attempt the allocation first. 1656 HeapWord* result = 1657 attempt_allocation_at_safepoint(word_size, 1658 context, 1659 false /* expect_null_mutator_alloc_region */); 1660 if (result != NULL) { 1661 assert(*succeeded, "sanity"); 1662 return result; 1663 } 1664 1665 // In a G1 heap, we're supposed to keep allocation from failing by 1666 // incremental pauses. Therefore, at least for now, we'll favor 1667 // expansion over collection. (This might change in the future if we can 1668 // do something smarter than full collection to satisfy a failed alloc.) 1669 result = expand_and_allocate(word_size, context); 1670 if (result != NULL) { 1671 assert(*succeeded, "sanity"); 1672 return result; 1673 } 1674 1675 // Expansion didn't work, we'll try to do a Full GC. 1676 bool gc_succeeded = do_collection(false, /* explicit_gc */ 1677 false, /* clear_all_soft_refs */ 1678 word_size); 1679 if (!gc_succeeded) { 1680 *succeeded = false; 1681 return NULL; 1682 } 1683 1684 // Retry the allocation 1685 result = attempt_allocation_at_safepoint(word_size, 1686 context, 1687 true /* expect_null_mutator_alloc_region */); 1688 if (result != NULL) { 1689 assert(*succeeded, "sanity"); 1690 return result; 1691 } 1692 1693 // Then, try a Full GC that will collect all soft references. 1694 gc_succeeded = do_collection(false, /* explicit_gc */ 1695 true, /* clear_all_soft_refs */ 1696 word_size); 1697 if (!gc_succeeded) { 1698 *succeeded = false; 1699 return NULL; 1700 } 1701 1702 // Retry the allocation once more 1703 result = attempt_allocation_at_safepoint(word_size, 1704 context, 1705 true /* expect_null_mutator_alloc_region */); 1706 if (result != NULL) { 1707 assert(*succeeded, "sanity"); 1708 return result; 1709 } 1710 1711 assert(!collector_policy()->should_clear_all_soft_refs(), 1712 "Flag should have been handled and cleared prior to this point"); 1713 1714 // What else? We might try synchronous finalization later. If the total 1715 // space available is large enough for the allocation, then a more 1716 // complete compaction phase than we've tried so far might be 1717 // appropriate. 1718 assert(*succeeded, "sanity"); 1719 return NULL; 1720 } 1721 1722 // Attempting to expand the heap sufficiently 1723 // to support an allocation of the given "word_size". If 1724 // successful, perform the allocation and return the address of the 1725 // allocated block, or else "NULL". 1726 1727 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) { 1728 assert_at_safepoint(true /* should_be_vm_thread */); 1729 1730 verify_region_sets_optional(); 1731 1732 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1733 ergo_verbose1(ErgoHeapSizing, 1734 "attempt heap expansion", 1735 ergo_format_reason("allocation request failed") 1736 ergo_format_byte("allocation request"), 1737 word_size * HeapWordSize); 1738 if (expand(expand_bytes)) { 1739 _hrm.verify_optional(); 1740 verify_region_sets_optional(); 1741 return attempt_allocation_at_safepoint(word_size, 1742 context, 1743 false /* expect_null_mutator_alloc_region */); 1744 } 1745 return NULL; 1746 } 1747 1748 bool G1CollectedHeap::expand(size_t expand_bytes) { 1749 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1750 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1751 HeapRegion::GrainBytes); 1752 ergo_verbose2(ErgoHeapSizing, 1753 "expand the heap", 1754 ergo_format_byte("requested expansion amount") 1755 ergo_format_byte("attempted expansion amount"), 1756 expand_bytes, aligned_expand_bytes); 1757 1758 if (is_maximal_no_gc()) { 1759 ergo_verbose0(ErgoHeapSizing, 1760 "did not expand the heap", 1761 ergo_format_reason("heap already fully expanded")); 1762 return false; 1763 } 1764 1765 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1766 assert(regions_to_expand > 0, "Must expand by at least one region"); 1767 1768 uint expanded_by = _hrm.expand_by(regions_to_expand); 1769 1770 if (expanded_by > 0) { 1771 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1772 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1773 g1_policy()->record_new_heap_size(num_regions()); 1774 } else { 1775 ergo_verbose0(ErgoHeapSizing, 1776 "did not expand the heap", 1777 ergo_format_reason("heap expansion operation failed")); 1778 // The expansion of the virtual storage space was unsuccessful. 1779 // Let's see if it was because we ran out of swap. 1780 if (G1ExitOnExpansionFailure && 1781 _hrm.available() >= regions_to_expand) { 1782 // We had head room... 1783 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1784 } 1785 } 1786 return regions_to_expand > 0; 1787 } 1788 1789 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1790 size_t aligned_shrink_bytes = 1791 ReservedSpace::page_align_size_down(shrink_bytes); 1792 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1793 HeapRegion::GrainBytes); 1794 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1795 1796 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1797 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1798 1799 ergo_verbose3(ErgoHeapSizing, 1800 "shrink the heap", 1801 ergo_format_byte("requested shrinking amount") 1802 ergo_format_byte("aligned shrinking amount") 1803 ergo_format_byte("attempted shrinking amount"), 1804 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1805 if (num_regions_removed > 0) { 1806 g1_policy()->record_new_heap_size(num_regions()); 1807 } else { 1808 ergo_verbose0(ErgoHeapSizing, 1809 "did not shrink the heap", 1810 ergo_format_reason("heap shrinking operation failed")); 1811 } 1812 } 1813 1814 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1815 verify_region_sets_optional(); 1816 1817 // We should only reach here at the end of a Full GC which means we 1818 // should not not be holding to any GC alloc regions. The method 1819 // below will make sure of that and do any remaining clean up. 1820 _allocator->abandon_gc_alloc_regions(); 1821 1822 // Instead of tearing down / rebuilding the free lists here, we 1823 // could instead use the remove_all_pending() method on free_list to 1824 // remove only the ones that we need to remove. 1825 tear_down_region_sets(true /* free_list_only */); 1826 shrink_helper(shrink_bytes); 1827 rebuild_region_sets(true /* free_list_only */); 1828 1829 _hrm.verify_optional(); 1830 verify_region_sets_optional(); 1831 } 1832 1833 // Public methods. 1834 1835 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away 1836 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list 1837 #endif // _MSC_VER 1838 1839 1840 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) : 1841 SharedHeap(policy_), 1842 _g1_policy(policy_), 1843 _dirty_card_queue_set(false), 1844 _into_cset_dirty_card_queue_set(false), 1845 _is_alive_closure_cm(this), 1846 _is_alive_closure_stw(this), 1847 _ref_processor_cm(NULL), 1848 _ref_processor_stw(NULL), 1849 _bot_shared(NULL), 1850 _evac_failure_scan_stack(NULL), 1851 _mark_in_progress(false), 1852 _cg1r(NULL), 1853 _g1mm(NULL), 1854 _refine_cte_cl(NULL), 1855 _full_collection(false), 1856 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1857 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1858 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1859 _humongous_reclaim_candidates(), 1860 _has_humongous_reclaim_candidates(false), 1861 _free_regions_coming(false), 1862 _young_list(new YoungList(this)), 1863 _gc_time_stamp(0), 1864 _survivor_plab_stats(YoungPLABSize, PLABWeight), 1865 _old_plab_stats(OldPLABSize, PLABWeight), 1866 _expand_heap_after_alloc_failure(true), 1867 _surviving_young_words(NULL), 1868 _old_marking_cycles_started(0), 1869 _old_marking_cycles_completed(0), 1870 _concurrent_cycle_started(false), 1871 _heap_summary_sent(false), 1872 _in_cset_fast_test(), 1873 _dirty_cards_region_list(NULL), 1874 _worker_cset_start_region(NULL), 1875 _worker_cset_start_region_time_stamp(NULL), 1876 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1877 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()), 1878 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1879 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) { 1880 1881 _g1h = this; 1882 1883 _allocator = G1Allocator::create_allocator(_g1h); 1884 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2; 1885 1886 int n_queues = MAX2((int)ParallelGCThreads, 1); 1887 _task_queues = new RefToScanQueueSet(n_queues); 1888 1889 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets(); 1890 assert(n_rem_sets > 0, "Invariant."); 1891 1892 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC); 1893 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(uint, n_queues, mtGC); 1894 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1895 1896 for (int i = 0; i < n_queues; i++) { 1897 RefToScanQueue* q = new RefToScanQueue(); 1898 q->initialize(); 1899 _task_queues->register_queue(i, q); 1900 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1901 } 1902 clear_cset_start_regions(); 1903 1904 // Initialize the G1EvacuationFailureALot counters and flags. 1905 NOT_PRODUCT(reset_evacuation_should_fail();) 1906 1907 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1908 } 1909 1910 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description, 1911 size_t size, 1912 size_t translation_factor) { 1913 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1); 1914 // Allocate a new reserved space, preferring to use large pages. 1915 ReservedSpace rs(size, preferred_page_size); 1916 G1RegionToSpaceMapper* result = 1917 G1RegionToSpaceMapper::create_mapper(rs, 1918 size, 1919 rs.alignment(), 1920 HeapRegion::GrainBytes, 1921 translation_factor, 1922 mtGC); 1923 if (TracePageSizes) { 1924 gclog_or_tty->print_cr("G1 '%s': pg_sz=" SIZE_FORMAT " base=" PTR_FORMAT " size=" SIZE_FORMAT " alignment=" SIZE_FORMAT " reqsize=" SIZE_FORMAT, 1925 description, preferred_page_size, p2i(rs.base()), rs.size(), rs.alignment(), size); 1926 } 1927 return result; 1928 } 1929 1930 jint G1CollectedHeap::initialize() { 1931 CollectedHeap::pre_initialize(); 1932 os::enable_vtime(); 1933 1934 G1Log::init(); 1935 1936 // Necessary to satisfy locking discipline assertions. 1937 1938 MutexLocker x(Heap_lock); 1939 1940 // We have to initialize the printer before committing the heap, as 1941 // it will be used then. 1942 _hr_printer.set_active(G1PrintHeapRegions); 1943 1944 // While there are no constraints in the GC code that HeapWordSize 1945 // be any particular value, there are multiple other areas in the 1946 // system which believe this to be true (e.g. oop->object_size in some 1947 // cases incorrectly returns the size in wordSize units rather than 1948 // HeapWordSize). 1949 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1950 1951 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1952 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1953 size_t heap_alignment = collector_policy()->heap_alignment(); 1954 1955 // Ensure that the sizes are properly aligned. 1956 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1957 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1958 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1959 1960 _refine_cte_cl = new RefineCardTableEntryClosure(); 1961 1962 _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl); 1963 1964 // Reserve the maximum. 1965 1966 // When compressed oops are enabled, the preferred heap base 1967 // is calculated by subtracting the requested size from the 1968 // 32Gb boundary and using the result as the base address for 1969 // heap reservation. If the requested size is not aligned to 1970 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1971 // into the ReservedHeapSpace constructor) then the actual 1972 // base of the reserved heap may end up differing from the 1973 // address that was requested (i.e. the preferred heap base). 1974 // If this happens then we could end up using a non-optimal 1975 // compressed oops mode. 1976 1977 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1978 heap_alignment); 1979 1980 // It is important to do this in a way such that concurrent readers can't 1981 // temporarily think something is in the heap. (I've actually seen this 1982 // happen in asserts: DLD.) 1983 _reserved.set_word_size(0); 1984 _reserved.set_start((HeapWord*)heap_rs.base()); 1985 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size())); 1986 1987 // Create the gen rem set (and barrier set) for the entire reserved region. 1988 _rem_set = collector_policy()->create_rem_set(_reserved, 2); 1989 set_barrier_set(rem_set()->bs()); 1990 if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) { 1991 vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS"); 1992 return JNI_ENOMEM; 1993 } 1994 1995 // Also create a G1 rem set. 1996 _g1_rem_set = new G1RemSet(this, g1_barrier_set()); 1997 1998 // Carve out the G1 part of the heap. 1999 2000 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 2001 G1RegionToSpaceMapper* heap_storage = 2002 G1RegionToSpaceMapper::create_mapper(g1_rs, 2003 g1_rs.size(), 2004 UseLargePages ? os::large_page_size() : os::vm_page_size(), 2005 HeapRegion::GrainBytes, 2006 1, 2007 mtJavaHeap); 2008 heap_storage->set_mapping_changed_listener(&_listener); 2009 2010 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps. 2011 G1RegionToSpaceMapper* bot_storage = 2012 create_aux_memory_mapper("Block offset table", 2013 G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize), 2014 G1BlockOffsetSharedArray::N_bytes); 2015 2016 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize)); 2017 G1RegionToSpaceMapper* cardtable_storage = 2018 create_aux_memory_mapper("Card table", 2019 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize), 2020 G1BlockOffsetSharedArray::N_bytes); 2021 2022 G1RegionToSpaceMapper* card_counts_storage = 2023 create_aux_memory_mapper("Card counts table", 2024 G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize), 2025 G1BlockOffsetSharedArray::N_bytes); 2026 2027 size_t bitmap_size = CMBitMap::compute_size(g1_rs.size()); 2028 G1RegionToSpaceMapper* prev_bitmap_storage = 2029 create_aux_memory_mapper("Prev Bitmap", bitmap_size, CMBitMap::mark_distance()); 2030 G1RegionToSpaceMapper* next_bitmap_storage = 2031 create_aux_memory_mapper("Next Bitmap", bitmap_size, CMBitMap::mark_distance()); 2032 2033 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 2034 g1_barrier_set()->initialize(cardtable_storage); 2035 // Do later initialization work for concurrent refinement. 2036 _cg1r->init(card_counts_storage); 2037 2038 // 6843694 - ensure that the maximum region index can fit 2039 // in the remembered set structures. 2040 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 2041 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 2042 2043 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 2044 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 2045 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 2046 "too many cards per region"); 2047 2048 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 2049 2050 _bot_shared = new G1BlockOffsetSharedArray(_reserved, bot_storage); 2051 2052 _g1h = this; 2053 2054 { 2055 HeapWord* start = _hrm.reserved().start(); 2056 HeapWord* end = _hrm.reserved().end(); 2057 size_t granularity = HeapRegion::GrainBytes; 2058 2059 _in_cset_fast_test.initialize(start, end, granularity); 2060 _humongous_reclaim_candidates.initialize(start, end, granularity); 2061 } 2062 2063 // Create the ConcurrentMark data structure and thread. 2064 // (Must do this late, so that "max_regions" is defined.) 2065 _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 2066 if (_cm == NULL || !_cm->completed_initialization()) { 2067 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark"); 2068 return JNI_ENOMEM; 2069 } 2070 _cmThread = _cm->cmThread(); 2071 2072 // Initialize the from_card cache structure of HeapRegionRemSet. 2073 HeapRegionRemSet::init_heap(max_regions()); 2074 2075 // Now expand into the initial heap size. 2076 if (!expand(init_byte_size)) { 2077 vm_shutdown_during_initialization("Failed to allocate initial heap."); 2078 return JNI_ENOMEM; 2079 } 2080 2081 // Perform any initialization actions delegated to the policy. 2082 g1_policy()->init(); 2083 2084 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 2085 SATB_Q_FL_lock, 2086 G1SATBProcessCompletedThreshold, 2087 Shared_SATB_Q_lock); 2088 2089 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl, 2090 DirtyCardQ_CBL_mon, 2091 DirtyCardQ_FL_lock, 2092 concurrent_g1_refine()->yellow_zone(), 2093 concurrent_g1_refine()->red_zone(), 2094 Shared_DirtyCardQ_lock); 2095 2096 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code 2097 DirtyCardQ_CBL_mon, 2098 DirtyCardQ_FL_lock, 2099 -1, // never trigger processing 2100 -1, // no limit on length 2101 Shared_DirtyCardQ_lock, 2102 &JavaThread::dirty_card_queue_set()); 2103 2104 // Initialize the card queue set used to hold cards containing 2105 // references into the collection set. 2106 _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code 2107 DirtyCardQ_CBL_mon, 2108 DirtyCardQ_FL_lock, 2109 -1, // never trigger processing 2110 -1, // no limit on length 2111 Shared_DirtyCardQ_lock, 2112 &JavaThread::dirty_card_queue_set()); 2113 2114 // In case we're keeping closure specialization stats, initialize those 2115 // counts and that mechanism. 2116 SpecializationStats::clear(); 2117 2118 // Here we allocate the dummy HeapRegion that is required by the 2119 // G1AllocRegion class. 2120 HeapRegion* dummy_region = _hrm.get_dummy_region(); 2121 2122 // We'll re-use the same region whether the alloc region will 2123 // require BOT updates or not and, if it doesn't, then a non-young 2124 // region will complain that it cannot support allocations without 2125 // BOT updates. So we'll tag the dummy region as eden to avoid that. 2126 dummy_region->set_eden(); 2127 // Make sure it's full. 2128 dummy_region->set_top(dummy_region->end()); 2129 G1AllocRegion::setup(this, dummy_region); 2130 2131 _allocator->init_mutator_alloc_region(); 2132 2133 // Do create of the monitoring and management support so that 2134 // values in the heap have been properly initialized. 2135 _g1mm = new G1MonitoringSupport(this); 2136 2137 G1StringDedup::initialize(); 2138 2139 return JNI_OK; 2140 } 2141 2142 void G1CollectedHeap::stop() { 2143 // Stop all concurrent threads. We do this to make sure these threads 2144 // do not continue to execute and access resources (e.g. gclog_or_tty) 2145 // that are destroyed during shutdown. 2146 _cg1r->stop(); 2147 _cmThread->stop(); 2148 if (G1StringDedup::is_enabled()) { 2149 G1StringDedup::stop(); 2150 } 2151 } 2152 2153 size_t G1CollectedHeap::conservative_max_heap_alignment() { 2154 return HeapRegion::max_region_size(); 2155 } 2156 2157 void G1CollectedHeap::ref_processing_init() { 2158 // Reference processing in G1 currently works as follows: 2159 // 2160 // * There are two reference processor instances. One is 2161 // used to record and process discovered references 2162 // during concurrent marking; the other is used to 2163 // record and process references during STW pauses 2164 // (both full and incremental). 2165 // * Both ref processors need to 'span' the entire heap as 2166 // the regions in the collection set may be dotted around. 2167 // 2168 // * For the concurrent marking ref processor: 2169 // * Reference discovery is enabled at initial marking. 2170 // * Reference discovery is disabled and the discovered 2171 // references processed etc during remarking. 2172 // * Reference discovery is MT (see below). 2173 // * Reference discovery requires a barrier (see below). 2174 // * Reference processing may or may not be MT 2175 // (depending on the value of ParallelRefProcEnabled 2176 // and ParallelGCThreads). 2177 // * A full GC disables reference discovery by the CM 2178 // ref processor and abandons any entries on it's 2179 // discovered lists. 2180 // 2181 // * For the STW processor: 2182 // * Non MT discovery is enabled at the start of a full GC. 2183 // * Processing and enqueueing during a full GC is non-MT. 2184 // * During a full GC, references are processed after marking. 2185 // 2186 // * Discovery (may or may not be MT) is enabled at the start 2187 // of an incremental evacuation pause. 2188 // * References are processed near the end of a STW evacuation pause. 2189 // * For both types of GC: 2190 // * Discovery is atomic - i.e. not concurrent. 2191 // * Reference discovery will not need a barrier. 2192 2193 SharedHeap::ref_processing_init(); 2194 MemRegion mr = reserved_region(); 2195 2196 // Concurrent Mark ref processor 2197 _ref_processor_cm = 2198 new ReferenceProcessor(mr, // span 2199 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2200 // mt processing 2201 (int) ParallelGCThreads, 2202 // degree of mt processing 2203 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 2204 // mt discovery 2205 (int) MAX2(ParallelGCThreads, ConcGCThreads), 2206 // degree of mt discovery 2207 false, 2208 // Reference discovery is not atomic 2209 &_is_alive_closure_cm); 2210 // is alive closure 2211 // (for efficiency/performance) 2212 2213 // STW ref processor 2214 _ref_processor_stw = 2215 new ReferenceProcessor(mr, // span 2216 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2217 // mt processing 2218 MAX2((int)ParallelGCThreads, 1), 2219 // degree of mt processing 2220 (ParallelGCThreads > 1), 2221 // mt discovery 2222 MAX2((int)ParallelGCThreads, 1), 2223 // degree of mt discovery 2224 true, 2225 // Reference discovery is atomic 2226 &_is_alive_closure_stw); 2227 // is alive closure 2228 // (for efficiency/performance) 2229 } 2230 2231 size_t G1CollectedHeap::capacity() const { 2232 return _hrm.length() * HeapRegion::GrainBytes; 2233 } 2234 2235 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 2236 assert(!hr->continuesHumongous(), "pre-condition"); 2237 hr->reset_gc_time_stamp(); 2238 if (hr->startsHumongous()) { 2239 uint first_index = hr->hrm_index() + 1; 2240 uint last_index = hr->last_hc_index(); 2241 for (uint i = first_index; i < last_index; i += 1) { 2242 HeapRegion* chr = region_at(i); 2243 assert(chr->continuesHumongous(), "sanity"); 2244 chr->reset_gc_time_stamp(); 2245 } 2246 } 2247 } 2248 2249 #ifndef PRODUCT 2250 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 2251 private: 2252 unsigned _gc_time_stamp; 2253 bool _failures; 2254 2255 public: 2256 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 2257 _gc_time_stamp(gc_time_stamp), _failures(false) { } 2258 2259 virtual bool doHeapRegion(HeapRegion* hr) { 2260 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 2261 if (_gc_time_stamp != region_gc_time_stamp) { 2262 gclog_or_tty->print_cr("Region " HR_FORMAT " has GC time stamp = %d, " 2263 "expected %d", HR_FORMAT_PARAMS(hr), 2264 region_gc_time_stamp, _gc_time_stamp); 2265 _failures = true; 2266 } 2267 return false; 2268 } 2269 2270 bool failures() { return _failures; } 2271 }; 2272 2273 void G1CollectedHeap::check_gc_time_stamps() { 2274 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 2275 heap_region_iterate(&cl); 2276 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2277 } 2278 #endif // PRODUCT 2279 2280 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, 2281 DirtyCardQueue* into_cset_dcq, 2282 bool concurrent, 2283 uint worker_i) { 2284 // Clean cards in the hot card cache 2285 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 2286 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq); 2287 2288 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2289 size_t n_completed_buffers = 0; 2290 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2291 n_completed_buffers++; 2292 } 2293 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers); 2294 dcqs.clear_n_completed_buffers(); 2295 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2296 } 2297 2298 2299 // Computes the sum of the storage used by the various regions. 2300 size_t G1CollectedHeap::used() const { 2301 return _allocator->used(); 2302 } 2303 2304 size_t G1CollectedHeap::used_unlocked() const { 2305 return _allocator->used_unlocked(); 2306 } 2307 2308 class SumUsedClosure: public HeapRegionClosure { 2309 size_t _used; 2310 public: 2311 SumUsedClosure() : _used(0) {} 2312 bool doHeapRegion(HeapRegion* r) { 2313 if (!r->continuesHumongous()) { 2314 _used += r->used(); 2315 } 2316 return false; 2317 } 2318 size_t result() { return _used; } 2319 }; 2320 2321 size_t G1CollectedHeap::recalculate_used() const { 2322 double recalculate_used_start = os::elapsedTime(); 2323 2324 SumUsedClosure blk; 2325 heap_region_iterate(&blk); 2326 2327 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2328 return blk.result(); 2329 } 2330 2331 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2332 switch (cause) { 2333 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2334 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2335 case GCCause::_g1_humongous_allocation: return true; 2336 case GCCause::_update_allocation_context_stats_inc: return true; 2337 case GCCause::_wb_conc_mark: return true; 2338 default: return false; 2339 } 2340 } 2341 2342 #ifndef PRODUCT 2343 void G1CollectedHeap::allocate_dummy_regions() { 2344 // Let's fill up most of the region 2345 size_t word_size = HeapRegion::GrainWords - 1024; 2346 // And as a result the region we'll allocate will be humongous. 2347 guarantee(isHumongous(word_size), "sanity"); 2348 2349 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2350 // Let's use the existing mechanism for the allocation 2351 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2352 AllocationContext::system()); 2353 if (dummy_obj != NULL) { 2354 MemRegion mr(dummy_obj, word_size); 2355 CollectedHeap::fill_with_object(mr); 2356 } else { 2357 // If we can't allocate once, we probably cannot allocate 2358 // again. Let's get out of the loop. 2359 break; 2360 } 2361 } 2362 } 2363 #endif // !PRODUCT 2364 2365 void G1CollectedHeap::increment_old_marking_cycles_started() { 2366 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2367 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2368 err_msg("Wrong marking cycle count (started: %d, completed: %d)", 2369 _old_marking_cycles_started, _old_marking_cycles_completed)); 2370 2371 _old_marking_cycles_started++; 2372 } 2373 2374 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2375 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2376 2377 // We assume that if concurrent == true, then the caller is a 2378 // concurrent thread that was joined the Suspendible Thread 2379 // Set. If there's ever a cheap way to check this, we should add an 2380 // assert here. 2381 2382 // Given that this method is called at the end of a Full GC or of a 2383 // concurrent cycle, and those can be nested (i.e., a Full GC can 2384 // interrupt a concurrent cycle), the number of full collections 2385 // completed should be either one (in the case where there was no 2386 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2387 // behind the number of full collections started. 2388 2389 // This is the case for the inner caller, i.e. a Full GC. 2390 assert(concurrent || 2391 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2392 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2393 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u " 2394 "is inconsistent with _old_marking_cycles_completed = %u", 2395 _old_marking_cycles_started, _old_marking_cycles_completed)); 2396 2397 // This is the case for the outer caller, i.e. the concurrent cycle. 2398 assert(!concurrent || 2399 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2400 err_msg("for outer caller (concurrent cycle): " 2401 "_old_marking_cycles_started = %u " 2402 "is inconsistent with _old_marking_cycles_completed = %u", 2403 _old_marking_cycles_started, _old_marking_cycles_completed)); 2404 2405 _old_marking_cycles_completed += 1; 2406 2407 // We need to clear the "in_progress" flag in the CM thread before 2408 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2409 // is set) so that if a waiter requests another System.gc() it doesn't 2410 // incorrectly see that a marking cycle is still in progress. 2411 if (concurrent) { 2412 _cmThread->clear_in_progress(); 2413 } 2414 2415 // This notify_all() will ensure that a thread that called 2416 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2417 // and it's waiting for a full GC to finish will be woken up. It is 2418 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2419 FullGCCount_lock->notify_all(); 2420 } 2421 2422 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) { 2423 _concurrent_cycle_started = true; 2424 _gc_timer_cm->register_gc_start(start_time); 2425 2426 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start()); 2427 trace_heap_before_gc(_gc_tracer_cm); 2428 } 2429 2430 void G1CollectedHeap::register_concurrent_cycle_end() { 2431 if (_concurrent_cycle_started) { 2432 if (_cm->has_aborted()) { 2433 _gc_tracer_cm->report_concurrent_mode_failure(); 2434 } 2435 2436 _gc_timer_cm->register_gc_end(); 2437 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions()); 2438 2439 // Clear state variables to prepare for the next concurrent cycle. 2440 _concurrent_cycle_started = false; 2441 _heap_summary_sent = false; 2442 } 2443 } 2444 2445 void G1CollectedHeap::trace_heap_after_concurrent_cycle() { 2446 if (_concurrent_cycle_started) { 2447 // This function can be called when: 2448 // the cleanup pause is run 2449 // the concurrent cycle is aborted before the cleanup pause. 2450 // the concurrent cycle is aborted after the cleanup pause, 2451 // but before the concurrent cycle end has been registered. 2452 // Make sure that we only send the heap information once. 2453 if (!_heap_summary_sent) { 2454 trace_heap_after_gc(_gc_tracer_cm); 2455 _heap_summary_sent = true; 2456 } 2457 } 2458 } 2459 2460 G1YCType G1CollectedHeap::yc_type() { 2461 bool is_young = g1_policy()->gcs_are_young(); 2462 bool is_initial_mark = g1_policy()->during_initial_mark_pause(); 2463 bool is_during_mark = mark_in_progress(); 2464 2465 if (is_initial_mark) { 2466 return InitialMark; 2467 } else if (is_during_mark) { 2468 return DuringMark; 2469 } else if (is_young) { 2470 return Normal; 2471 } else { 2472 return Mixed; 2473 } 2474 } 2475 2476 void G1CollectedHeap::collect(GCCause::Cause cause) { 2477 assert_heap_not_locked(); 2478 2479 uint gc_count_before; 2480 uint old_marking_count_before; 2481 uint full_gc_count_before; 2482 bool retry_gc; 2483 2484 do { 2485 retry_gc = false; 2486 2487 { 2488 MutexLocker ml(Heap_lock); 2489 2490 // Read the GC count while holding the Heap_lock 2491 gc_count_before = total_collections(); 2492 full_gc_count_before = total_full_collections(); 2493 old_marking_count_before = _old_marking_cycles_started; 2494 } 2495 2496 if (should_do_concurrent_full_gc(cause)) { 2497 // Schedule an initial-mark evacuation pause that will start a 2498 // concurrent cycle. We're setting word_size to 0 which means that 2499 // we are not requesting a post-GC allocation. 2500 VM_G1IncCollectionPause op(gc_count_before, 2501 0, /* word_size */ 2502 true, /* should_initiate_conc_mark */ 2503 g1_policy()->max_pause_time_ms(), 2504 cause); 2505 op.set_allocation_context(AllocationContext::current()); 2506 2507 VMThread::execute(&op); 2508 if (!op.pause_succeeded()) { 2509 if (old_marking_count_before == _old_marking_cycles_started) { 2510 retry_gc = op.should_retry_gc(); 2511 } else { 2512 // A Full GC happened while we were trying to schedule the 2513 // initial-mark GC. No point in starting a new cycle given 2514 // that the whole heap was collected anyway. 2515 } 2516 2517 if (retry_gc) { 2518 if (GC_locker::is_active_and_needs_gc()) { 2519 GC_locker::stall_until_clear(); 2520 } 2521 } 2522 } 2523 } else { 2524 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2525 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2526 2527 // Schedule a standard evacuation pause. We're setting word_size 2528 // to 0 which means that we are not requesting a post-GC allocation. 2529 VM_G1IncCollectionPause op(gc_count_before, 2530 0, /* word_size */ 2531 false, /* should_initiate_conc_mark */ 2532 g1_policy()->max_pause_time_ms(), 2533 cause); 2534 VMThread::execute(&op); 2535 } else { 2536 // Schedule a Full GC. 2537 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2538 VMThread::execute(&op); 2539 } 2540 } 2541 } while (retry_gc); 2542 } 2543 2544 bool G1CollectedHeap::is_in(const void* p) const { 2545 if (_hrm.reserved().contains(p)) { 2546 // Given that we know that p is in the reserved space, 2547 // heap_region_containing_raw() should successfully 2548 // return the containing region. 2549 HeapRegion* hr = heap_region_containing_raw(p); 2550 return hr->is_in(p); 2551 } else { 2552 return false; 2553 } 2554 } 2555 2556 #ifdef ASSERT 2557 bool G1CollectedHeap::is_in_exact(const void* p) const { 2558 bool contains = reserved_region().contains(p); 2559 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2560 if (contains && available) { 2561 return true; 2562 } else { 2563 return false; 2564 } 2565 } 2566 #endif 2567 2568 // Iteration functions. 2569 2570 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion. 2571 2572 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2573 ExtendedOopClosure* _cl; 2574 public: 2575 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {} 2576 bool doHeapRegion(HeapRegion* r) { 2577 if (!r->continuesHumongous()) { 2578 r->oop_iterate(_cl); 2579 } 2580 return false; 2581 } 2582 }; 2583 2584 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) { 2585 IterateOopClosureRegionClosure blk(cl); 2586 heap_region_iterate(&blk); 2587 } 2588 2589 // Iterates an ObjectClosure over all objects within a HeapRegion. 2590 2591 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2592 ObjectClosure* _cl; 2593 public: 2594 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2595 bool doHeapRegion(HeapRegion* r) { 2596 if (! r->continuesHumongous()) { 2597 r->object_iterate(_cl); 2598 } 2599 return false; 2600 } 2601 }; 2602 2603 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2604 IterateObjectClosureRegionClosure blk(cl); 2605 heap_region_iterate(&blk); 2606 } 2607 2608 // Calls a SpaceClosure on a HeapRegion. 2609 2610 class SpaceClosureRegionClosure: public HeapRegionClosure { 2611 SpaceClosure* _cl; 2612 public: 2613 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {} 2614 bool doHeapRegion(HeapRegion* r) { 2615 _cl->do_space(r); 2616 return false; 2617 } 2618 }; 2619 2620 void G1CollectedHeap::space_iterate(SpaceClosure* cl) { 2621 SpaceClosureRegionClosure blk(cl); 2622 heap_region_iterate(&blk); 2623 } 2624 2625 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2626 _hrm.iterate(cl); 2627 } 2628 2629 void 2630 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl, 2631 uint worker_id, 2632 uint num_workers, 2633 jint claim_value) const { 2634 _hrm.par_iterate(cl, worker_id, num_workers, claim_value); 2635 } 2636 2637 class ResetClaimValuesClosure: public HeapRegionClosure { 2638 public: 2639 bool doHeapRegion(HeapRegion* r) { 2640 r->set_claim_value(HeapRegion::InitialClaimValue); 2641 return false; 2642 } 2643 }; 2644 2645 void G1CollectedHeap::reset_heap_region_claim_values() { 2646 ResetClaimValuesClosure blk; 2647 heap_region_iterate(&blk); 2648 } 2649 2650 void G1CollectedHeap::reset_cset_heap_region_claim_values() { 2651 ResetClaimValuesClosure blk; 2652 collection_set_iterate(&blk); 2653 } 2654 2655 #ifdef ASSERT 2656 // This checks whether all regions in the heap have the correct claim 2657 // value. I also piggy-backed on this a check to ensure that the 2658 // humongous_start_region() information on "continues humongous" 2659 // regions is correct. 2660 2661 class CheckClaimValuesClosure : public HeapRegionClosure { 2662 private: 2663 jint _claim_value; 2664 uint _failures; 2665 HeapRegion* _sh_region; 2666 2667 public: 2668 CheckClaimValuesClosure(jint claim_value) : 2669 _claim_value(claim_value), _failures(0), _sh_region(NULL) { } 2670 bool doHeapRegion(HeapRegion* r) { 2671 if (r->claim_value() != _claim_value) { 2672 gclog_or_tty->print_cr("Region " HR_FORMAT ", " 2673 "claim value = %d, should be %d", 2674 HR_FORMAT_PARAMS(r), 2675 r->claim_value(), _claim_value); 2676 ++_failures; 2677 } 2678 if (!r->isHumongous()) { 2679 _sh_region = NULL; 2680 } else if (r->startsHumongous()) { 2681 _sh_region = r; 2682 } else if (r->continuesHumongous()) { 2683 if (r->humongous_start_region() != _sh_region) { 2684 gclog_or_tty->print_cr("Region " HR_FORMAT ", " 2685 "HS = " PTR_FORMAT ", should be " PTR_FORMAT, 2686 HR_FORMAT_PARAMS(r), 2687 r->humongous_start_region(), 2688 _sh_region); 2689 ++_failures; 2690 } 2691 } 2692 return false; 2693 } 2694 uint failures() { return _failures; } 2695 }; 2696 2697 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) { 2698 CheckClaimValuesClosure cl(claim_value); 2699 heap_region_iterate(&cl); 2700 return cl.failures() == 0; 2701 } 2702 2703 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure { 2704 private: 2705 jint _claim_value; 2706 uint _failures; 2707 2708 public: 2709 CheckClaimValuesInCSetHRClosure(jint claim_value) : 2710 _claim_value(claim_value), _failures(0) { } 2711 2712 uint failures() { return _failures; } 2713 2714 bool doHeapRegion(HeapRegion* hr) { 2715 assert(hr->in_collection_set(), "how?"); 2716 assert(!hr->isHumongous(), "H-region in CSet"); 2717 if (hr->claim_value() != _claim_value) { 2718 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", " 2719 "claim value = %d, should be %d", 2720 HR_FORMAT_PARAMS(hr), 2721 hr->claim_value(), _claim_value); 2722 _failures += 1; 2723 } 2724 return false; 2725 } 2726 }; 2727 2728 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) { 2729 CheckClaimValuesInCSetHRClosure cl(claim_value); 2730 collection_set_iterate(&cl); 2731 return cl.failures() == 0; 2732 } 2733 #endif // ASSERT 2734 2735 // Clear the cached CSet starting regions and (more importantly) 2736 // the time stamps. Called when we reset the GC time stamp. 2737 void G1CollectedHeap::clear_cset_start_regions() { 2738 assert(_worker_cset_start_region != NULL, "sanity"); 2739 assert(_worker_cset_start_region_time_stamp != NULL, "sanity"); 2740 2741 int n_queues = MAX2((int)ParallelGCThreads, 1); 2742 for (int i = 0; i < n_queues; i++) { 2743 _worker_cset_start_region[i] = NULL; 2744 _worker_cset_start_region_time_stamp[i] = 0; 2745 } 2746 } 2747 2748 // Given the id of a worker, obtain or calculate a suitable 2749 // starting region for iterating over the current collection set. 2750 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) { 2751 assert(get_gc_time_stamp() > 0, "should have been updated by now"); 2752 2753 HeapRegion* result = NULL; 2754 unsigned gc_time_stamp = get_gc_time_stamp(); 2755 2756 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) { 2757 // Cached starting region for current worker was set 2758 // during the current pause - so it's valid. 2759 // Note: the cached starting heap region may be NULL 2760 // (when the collection set is empty). 2761 result = _worker_cset_start_region[worker_i]; 2762 assert(result == NULL || result->in_collection_set(), "sanity"); 2763 return result; 2764 } 2765 2766 // The cached entry was not valid so let's calculate 2767 // a suitable starting heap region for this worker. 2768 2769 // We want the parallel threads to start their collection 2770 // set iteration at different collection set regions to 2771 // avoid contention. 2772 // If we have: 2773 // n collection set regions 2774 // p threads 2775 // Then thread t will start at region floor ((t * n) / p) 2776 2777 result = g1_policy()->collection_set(); 2778 if (G1CollectedHeap::use_parallel_gc_threads()) { 2779 uint cs_size = g1_policy()->cset_region_length(); 2780 uint active_workers = workers()->active_workers(); 2781 assert(UseDynamicNumberOfGCThreads || 2782 active_workers == workers()->total_workers(), 2783 "Unless dynamic should use total workers"); 2784 2785 uint end_ind = (cs_size * worker_i) / active_workers; 2786 uint start_ind = 0; 2787 2788 if (worker_i > 0 && 2789 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) { 2790 // Previous workers starting region is valid 2791 // so let's iterate from there 2792 start_ind = (cs_size * (worker_i - 1)) / active_workers; 2793 result = _worker_cset_start_region[worker_i - 1]; 2794 } 2795 2796 for (uint i = start_ind; i < end_ind; i++) { 2797 result = result->next_in_collection_set(); 2798 } 2799 } 2800 2801 // Note: the calculated starting heap region may be NULL 2802 // (when the collection set is empty). 2803 assert(result == NULL || result->in_collection_set(), "sanity"); 2804 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp, 2805 "should be updated only once per pause"); 2806 _worker_cset_start_region[worker_i] = result; 2807 OrderAccess::storestore(); 2808 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp; 2809 return result; 2810 } 2811 2812 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2813 HeapRegion* r = g1_policy()->collection_set(); 2814 while (r != NULL) { 2815 HeapRegion* next = r->next_in_collection_set(); 2816 if (cl->doHeapRegion(r)) { 2817 cl->incomplete(); 2818 return; 2819 } 2820 r = next; 2821 } 2822 } 2823 2824 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r, 2825 HeapRegionClosure *cl) { 2826 if (r == NULL) { 2827 // The CSet is empty so there's nothing to do. 2828 return; 2829 } 2830 2831 assert(r->in_collection_set(), 2832 "Start region must be a member of the collection set."); 2833 HeapRegion* cur = r; 2834 while (cur != NULL) { 2835 HeapRegion* next = cur->next_in_collection_set(); 2836 if (cl->doHeapRegion(cur) && false) { 2837 cl->incomplete(); 2838 return; 2839 } 2840 cur = next; 2841 } 2842 cur = g1_policy()->collection_set(); 2843 while (cur != r) { 2844 HeapRegion* next = cur->next_in_collection_set(); 2845 if (cl->doHeapRegion(cur) && false) { 2846 cl->incomplete(); 2847 return; 2848 } 2849 cur = next; 2850 } 2851 } 2852 2853 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const { 2854 HeapRegion* result = _hrm.next_region_in_heap(from); 2855 while (result != NULL && result->isHumongous()) { 2856 result = _hrm.next_region_in_heap(result); 2857 } 2858 return result; 2859 } 2860 2861 Space* G1CollectedHeap::space_containing(const void* addr) const { 2862 return heap_region_containing(addr); 2863 } 2864 2865 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2866 Space* sp = space_containing(addr); 2867 return sp->block_start(addr); 2868 } 2869 2870 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2871 Space* sp = space_containing(addr); 2872 return sp->block_size(addr); 2873 } 2874 2875 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2876 Space* sp = space_containing(addr); 2877 return sp->block_is_obj(addr); 2878 } 2879 2880 bool G1CollectedHeap::supports_tlab_allocation() const { 2881 return true; 2882 } 2883 2884 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2885 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes; 2886 } 2887 2888 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2889 return young_list()->eden_used_bytes(); 2890 } 2891 2892 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2893 // must be smaller than the humongous object limit. 2894 size_t G1CollectedHeap::max_tlab_size() const { 2895 return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment); 2896 } 2897 2898 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2899 // Return the remaining space in the cur alloc region, but not less than 2900 // the min TLAB size. 2901 2902 // Also, this value can be at most the humongous object threshold, 2903 // since we can't allow tlabs to grow big enough to accommodate 2904 // humongous objects. 2905 2906 HeapRegion* hr = _allocator->mutator_alloc_region(AllocationContext::current())->get(); 2907 size_t max_tlab = max_tlab_size() * wordSize; 2908 if (hr == NULL) { 2909 return max_tlab; 2910 } else { 2911 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab); 2912 } 2913 } 2914 2915 size_t G1CollectedHeap::max_capacity() const { 2916 return _hrm.reserved().byte_size(); 2917 } 2918 2919 jlong G1CollectedHeap::millis_since_last_gc() { 2920 // assert(false, "NYI"); 2921 return 0; 2922 } 2923 2924 void G1CollectedHeap::prepare_for_verify() { 2925 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) { 2926 ensure_parsability(false); 2927 } 2928 g1_rem_set()->prepare_for_verify(); 2929 } 2930 2931 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr, 2932 VerifyOption vo) { 2933 switch (vo) { 2934 case VerifyOption_G1UsePrevMarking: 2935 return hr->obj_allocated_since_prev_marking(obj); 2936 case VerifyOption_G1UseNextMarking: 2937 return hr->obj_allocated_since_next_marking(obj); 2938 case VerifyOption_G1UseMarkWord: 2939 return false; 2940 default: 2941 ShouldNotReachHere(); 2942 } 2943 return false; // keep some compilers happy 2944 } 2945 2946 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) { 2947 switch (vo) { 2948 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start(); 2949 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start(); 2950 case VerifyOption_G1UseMarkWord: return NULL; 2951 default: ShouldNotReachHere(); 2952 } 2953 return NULL; // keep some compilers happy 2954 } 2955 2956 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) { 2957 switch (vo) { 2958 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj); 2959 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj); 2960 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked(); 2961 default: ShouldNotReachHere(); 2962 } 2963 return false; // keep some compilers happy 2964 } 2965 2966 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) { 2967 switch (vo) { 2968 case VerifyOption_G1UsePrevMarking: return "PTAMS"; 2969 case VerifyOption_G1UseNextMarking: return "NTAMS"; 2970 case VerifyOption_G1UseMarkWord: return "NONE"; 2971 default: ShouldNotReachHere(); 2972 } 2973 return NULL; // keep some compilers happy 2974 } 2975 2976 class VerifyRootsClosure: public OopClosure { 2977 private: 2978 G1CollectedHeap* _g1h; 2979 VerifyOption _vo; 2980 bool _failures; 2981 public: 2982 // _vo == UsePrevMarking -> use "prev" marking information, 2983 // _vo == UseNextMarking -> use "next" marking information, 2984 // _vo == UseMarkWord -> use mark word from object header. 2985 VerifyRootsClosure(VerifyOption vo) : 2986 _g1h(G1CollectedHeap::heap()), 2987 _vo(vo), 2988 _failures(false) { } 2989 2990 bool failures() { return _failures; } 2991 2992 template <class T> void do_oop_nv(T* p) { 2993 T heap_oop = oopDesc::load_heap_oop(p); 2994 if (!oopDesc::is_null(heap_oop)) { 2995 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 2996 if (_g1h->is_obj_dead_cond(obj, _vo)) { 2997 gclog_or_tty->print_cr("Root location " PTR_FORMAT " " 2998 "points to dead obj " PTR_FORMAT, p, (void*) obj); 2999 if (_vo == VerifyOption_G1UseMarkWord) { 3000 gclog_or_tty->print_cr(" Mark word: " PTR_FORMAT, (void*)(obj->mark())); 3001 } 3002 obj->print_on(gclog_or_tty); 3003 _failures = true; 3004 } 3005 } 3006 } 3007 3008 void do_oop(oop* p) { do_oop_nv(p); } 3009 void do_oop(narrowOop* p) { do_oop_nv(p); } 3010 }; 3011 3012 class G1VerifyCodeRootOopClosure: public OopClosure { 3013 G1CollectedHeap* _g1h; 3014 OopClosure* _root_cl; 3015 nmethod* _nm; 3016 VerifyOption _vo; 3017 bool _failures; 3018 3019 template <class T> void do_oop_work(T* p) { 3020 // First verify that this root is live 3021 _root_cl->do_oop(p); 3022 3023 if (!G1VerifyHeapRegionCodeRoots) { 3024 // We're not verifying the code roots attached to heap region. 3025 return; 3026 } 3027 3028 // Don't check the code roots during marking verification in a full GC 3029 if (_vo == VerifyOption_G1UseMarkWord) { 3030 return; 3031 } 3032 3033 // Now verify that the current nmethod (which contains p) is 3034 // in the code root list of the heap region containing the 3035 // object referenced by p. 3036 3037 T heap_oop = oopDesc::load_heap_oop(p); 3038 if (!oopDesc::is_null(heap_oop)) { 3039 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 3040 3041 // Now fetch the region containing the object 3042 HeapRegion* hr = _g1h->heap_region_containing(obj); 3043 HeapRegionRemSet* hrrs = hr->rem_set(); 3044 // Verify that the strong code root list for this region 3045 // contains the nmethod 3046 if (!hrrs->strong_code_roots_list_contains(_nm)) { 3047 gclog_or_tty->print_cr("Code root location " PTR_FORMAT " " 3048 "from nmethod " PTR_FORMAT " not in strong " 3049 "code roots for region [" PTR_FORMAT "," PTR_FORMAT ")", 3050 p, _nm, hr->bottom(), hr->end()); 3051 _failures = true; 3052 } 3053 } 3054 } 3055 3056 public: 3057 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo): 3058 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {} 3059 3060 void do_oop(oop* p) { do_oop_work(p); } 3061 void do_oop(narrowOop* p) { do_oop_work(p); } 3062 3063 void set_nmethod(nmethod* nm) { _nm = nm; } 3064 bool failures() { return _failures; } 3065 }; 3066 3067 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure { 3068 G1VerifyCodeRootOopClosure* _oop_cl; 3069 3070 public: 3071 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl): 3072 _oop_cl(oop_cl) {} 3073 3074 void do_code_blob(CodeBlob* cb) { 3075 nmethod* nm = cb->as_nmethod_or_null(); 3076 if (nm != NULL) { 3077 _oop_cl->set_nmethod(nm); 3078 nm->oops_do(_oop_cl); 3079 } 3080 } 3081 }; 3082 3083 class YoungRefCounterClosure : public OopClosure { 3084 G1CollectedHeap* _g1h; 3085 int _count; 3086 public: 3087 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {} 3088 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } } 3089 void do_oop(narrowOop* p) { ShouldNotReachHere(); } 3090 3091 int count() { return _count; } 3092 void reset_count() { _count = 0; }; 3093 }; 3094 3095 class VerifyKlassClosure: public KlassClosure { 3096 YoungRefCounterClosure _young_ref_counter_closure; 3097 OopClosure *_oop_closure; 3098 public: 3099 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {} 3100 void do_klass(Klass* k) { 3101 k->oops_do(_oop_closure); 3102 3103 _young_ref_counter_closure.reset_count(); 3104 k->oops_do(&_young_ref_counter_closure); 3105 if (_young_ref_counter_closure.count() > 0) { 3106 guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k)); 3107 } 3108 } 3109 }; 3110 3111 class VerifyLivenessOopClosure: public OopClosure { 3112 G1CollectedHeap* _g1h; 3113 VerifyOption _vo; 3114 public: 3115 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo): 3116 _g1h(g1h), _vo(vo) 3117 { } 3118 void do_oop(narrowOop *p) { do_oop_work(p); } 3119 void do_oop( oop *p) { do_oop_work(p); } 3120 3121 template <class T> void do_oop_work(T *p) { 3122 oop obj = oopDesc::load_decode_heap_oop(p); 3123 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo), 3124 "Dead object referenced by a not dead object"); 3125 } 3126 }; 3127 3128 class VerifyObjsInRegionClosure: public ObjectClosure { 3129 private: 3130 G1CollectedHeap* _g1h; 3131 size_t _live_bytes; 3132 HeapRegion *_hr; 3133 VerifyOption _vo; 3134 public: 3135 // _vo == UsePrevMarking -> use "prev" marking information, 3136 // _vo == UseNextMarking -> use "next" marking information, 3137 // _vo == UseMarkWord -> use mark word from object header. 3138 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo) 3139 : _live_bytes(0), _hr(hr), _vo(vo) { 3140 _g1h = G1CollectedHeap::heap(); 3141 } 3142 void do_object(oop o) { 3143 VerifyLivenessOopClosure isLive(_g1h, _vo); 3144 assert(o != NULL, "Huh?"); 3145 if (!_g1h->is_obj_dead_cond(o, _vo)) { 3146 // If the object is alive according to the mark word, 3147 // then verify that the marking information agrees. 3148 // Note we can't verify the contra-positive of the 3149 // above: if the object is dead (according to the mark 3150 // word), it may not be marked, or may have been marked 3151 // but has since became dead, or may have been allocated 3152 // since the last marking. 3153 if (_vo == VerifyOption_G1UseMarkWord) { 3154 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch"); 3155 } 3156 3157 o->oop_iterate_no_header(&isLive); 3158 if (!_hr->obj_allocated_since_prev_marking(o)) { 3159 size_t obj_size = o->size(); // Make sure we don't overflow 3160 _live_bytes += (obj_size * HeapWordSize); 3161 } 3162 } 3163 } 3164 size_t live_bytes() { return _live_bytes; } 3165 }; 3166 3167 class PrintObjsInRegionClosure : public ObjectClosure { 3168 HeapRegion *_hr; 3169 G1CollectedHeap *_g1; 3170 public: 3171 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) { 3172 _g1 = G1CollectedHeap::heap(); 3173 }; 3174 3175 void do_object(oop o) { 3176 if (o != NULL) { 3177 HeapWord *start = (HeapWord *) o; 3178 size_t word_sz = o->size(); 3179 gclog_or_tty->print("\nPrinting obj " PTR_FORMAT " of size " SIZE_FORMAT 3180 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n", 3181 (void*) o, word_sz, 3182 _g1->isMarkedPrev(o), 3183 _g1->isMarkedNext(o), 3184 _hr->obj_allocated_since_prev_marking(o)); 3185 HeapWord *end = start + word_sz; 3186 HeapWord *cur; 3187 int *val; 3188 for (cur = start; cur < end; cur++) { 3189 val = (int *) cur; 3190 gclog_or_tty->print("\t " PTR_FORMAT ":" PTR_FORMAT "\n", val, *val); 3191 } 3192 } 3193 } 3194 }; 3195 3196 class VerifyRegionClosure: public HeapRegionClosure { 3197 private: 3198 bool _par; 3199 VerifyOption _vo; 3200 bool _failures; 3201 public: 3202 // _vo == UsePrevMarking -> use "prev" marking information, 3203 // _vo == UseNextMarking -> use "next" marking information, 3204 // _vo == UseMarkWord -> use mark word from object header. 3205 VerifyRegionClosure(bool par, VerifyOption vo) 3206 : _par(par), 3207 _vo(vo), 3208 _failures(false) {} 3209 3210 bool failures() { 3211 return _failures; 3212 } 3213 3214 bool doHeapRegion(HeapRegion* r) { 3215 if (!r->continuesHumongous()) { 3216 bool failures = false; 3217 r->verify(_vo, &failures); 3218 if (failures) { 3219 _failures = true; 3220 } else { 3221 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo); 3222 r->object_iterate(¬_dead_yet_cl); 3223 if (_vo != VerifyOption_G1UseNextMarking) { 3224 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) { 3225 gclog_or_tty->print_cr("[" PTR_FORMAT "," PTR_FORMAT "] " 3226 "max_live_bytes " SIZE_FORMAT " " 3227 "< calculated " SIZE_FORMAT, 3228 r->bottom(), r->end(), 3229 r->max_live_bytes(), 3230 not_dead_yet_cl.live_bytes()); 3231 _failures = true; 3232 } 3233 } else { 3234 // When vo == UseNextMarking we cannot currently do a sanity 3235 // check on the live bytes as the calculation has not been 3236 // finalized yet. 3237 } 3238 } 3239 } 3240 return false; // stop the region iteration if we hit a failure 3241 } 3242 }; 3243 3244 // This is the task used for parallel verification of the heap regions 3245 3246 class G1ParVerifyTask: public AbstractGangTask { 3247 private: 3248 G1CollectedHeap* _g1h; 3249 VerifyOption _vo; 3250 bool _failures; 3251 3252 public: 3253 // _vo == UsePrevMarking -> use "prev" marking information, 3254 // _vo == UseNextMarking -> use "next" marking information, 3255 // _vo == UseMarkWord -> use mark word from object header. 3256 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) : 3257 AbstractGangTask("Parallel verify task"), 3258 _g1h(g1h), 3259 _vo(vo), 3260 _failures(false) { } 3261 3262 bool failures() { 3263 return _failures; 3264 } 3265 3266 void work(uint worker_id) { 3267 HandleMark hm; 3268 VerifyRegionClosure blk(true, _vo); 3269 _g1h->heap_region_par_iterate_chunked(&blk, worker_id, 3270 _g1h->workers()->active_workers(), 3271 HeapRegion::ParVerifyClaimValue); 3272 if (blk.failures()) { 3273 _failures = true; 3274 } 3275 } 3276 }; 3277 3278 void G1CollectedHeap::verify(bool silent, VerifyOption vo) { 3279 if (SafepointSynchronize::is_at_safepoint()) { 3280 assert(Thread::current()->is_VM_thread(), 3281 "Expected to be executed serially by the VM thread at this point"); 3282 3283 if (!silent) { gclog_or_tty->print("Roots "); } 3284 VerifyRootsClosure rootsCl(vo); 3285 VerifyKlassClosure klassCl(this, &rootsCl); 3286 CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false); 3287 3288 // We apply the relevant closures to all the oops in the 3289 // system dictionary, class loader data graph, the string table 3290 // and the nmethods in the code cache. 3291 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo); 3292 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl); 3293 3294 { 3295 G1RootProcessor root_processor(this); 3296 root_processor.process_all_roots(&rootsCl, 3297 &cldCl, 3298 &blobsCl); 3299 } 3300 3301 bool failures = rootsCl.failures() || codeRootsCl.failures(); 3302 3303 if (vo != VerifyOption_G1UseMarkWord) { 3304 // If we're verifying during a full GC then the region sets 3305 // will have been torn down at the start of the GC. Therefore 3306 // verifying the region sets will fail. So we only verify 3307 // the region sets when not in a full GC. 3308 if (!silent) { gclog_or_tty->print("HeapRegionSets "); } 3309 verify_region_sets(); 3310 } 3311 3312 if (!silent) { gclog_or_tty->print("HeapRegions "); } 3313 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) { 3314 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue), 3315 "sanity check"); 3316 3317 G1ParVerifyTask task(this, vo); 3318 assert(UseDynamicNumberOfGCThreads || 3319 workers()->active_workers() == workers()->total_workers(), 3320 "If not dynamic should be using all the workers"); 3321 int n_workers = workers()->active_workers(); 3322 set_par_threads(n_workers); 3323 workers()->run_task(&task); 3324 set_par_threads(0); 3325 if (task.failures()) { 3326 failures = true; 3327 } 3328 3329 // Checks that the expected amount of parallel work was done. 3330 // The implication is that n_workers is > 0. 3331 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue), 3332 "sanity check"); 3333 3334 reset_heap_region_claim_values(); 3335 3336 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue), 3337 "sanity check"); 3338 } else { 3339 VerifyRegionClosure blk(false, vo); 3340 heap_region_iterate(&blk); 3341 if (blk.failures()) { 3342 failures = true; 3343 } 3344 } 3345 if (!silent) gclog_or_tty->print("RemSet "); 3346 rem_set()->verify(); 3347 3348 if (G1StringDedup::is_enabled()) { 3349 if (!silent) gclog_or_tty->print("StrDedup "); 3350 G1StringDedup::verify(); 3351 } 3352 3353 if (failures) { 3354 gclog_or_tty->print_cr("Heap:"); 3355 // It helps to have the per-region information in the output to 3356 // help us track down what went wrong. This is why we call 3357 // print_extended_on() instead of print_on(). 3358 print_extended_on(gclog_or_tty); 3359 gclog_or_tty->cr(); 3360 #ifndef PRODUCT 3361 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) { 3362 concurrent_mark()->print_reachable("at-verification-failure", 3363 vo, false /* all */); 3364 } 3365 #endif 3366 gclog_or_tty->flush(); 3367 } 3368 guarantee(!failures, "there should not have been any failures"); 3369 } else { 3370 if (!silent) { 3371 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet"); 3372 if (G1StringDedup::is_enabled()) { 3373 gclog_or_tty->print(", StrDedup"); 3374 } 3375 gclog_or_tty->print(") "); 3376 } 3377 } 3378 } 3379 3380 void G1CollectedHeap::verify(bool silent) { 3381 verify(silent, VerifyOption_G1UsePrevMarking); 3382 } 3383 3384 double G1CollectedHeap::verify(bool guard, const char* msg) { 3385 double verify_time_ms = 0.0; 3386 3387 if (guard && total_collections() >= VerifyGCStartAt) { 3388 double verify_start = os::elapsedTime(); 3389 HandleMark hm; // Discard invalid handles created during verification 3390 prepare_for_verify(); 3391 Universe::verify(VerifyOption_G1UsePrevMarking, msg); 3392 verify_time_ms = (os::elapsedTime() - verify_start) * 1000; 3393 } 3394 3395 return verify_time_ms; 3396 } 3397 3398 void G1CollectedHeap::verify_before_gc() { 3399 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:"); 3400 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms); 3401 } 3402 3403 void G1CollectedHeap::verify_after_gc() { 3404 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:"); 3405 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms); 3406 } 3407 3408 class PrintRegionClosure: public HeapRegionClosure { 3409 outputStream* _st; 3410 public: 3411 PrintRegionClosure(outputStream* st) : _st(st) {} 3412 bool doHeapRegion(HeapRegion* r) { 3413 r->print_on(_st); 3414 return false; 3415 } 3416 }; 3417 3418 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3419 const HeapRegion* hr, 3420 const VerifyOption vo) const { 3421 switch (vo) { 3422 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 3423 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 3424 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked(); 3425 default: ShouldNotReachHere(); 3426 } 3427 return false; // keep some compilers happy 3428 } 3429 3430 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3431 const VerifyOption vo) const { 3432 switch (vo) { 3433 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 3434 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 3435 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked(); 3436 default: ShouldNotReachHere(); 3437 } 3438 return false; // keep some compilers happy 3439 } 3440 3441 void G1CollectedHeap::print_on(outputStream* st) const { 3442 st->print(" %-20s", "garbage-first heap"); 3443 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 3444 capacity()/K, used_unlocked()/K); 3445 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")", 3446 _hrm.reserved().start(), 3447 _hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords, 3448 _hrm.reserved().end()); 3449 st->cr(); 3450 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 3451 uint young_regions = _young_list->length(); 3452 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 3453 (size_t) young_regions * HeapRegion::GrainBytes / K); 3454 uint survivor_regions = g1_policy()->recorded_survivor_regions(); 3455 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 3456 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 3457 st->cr(); 3458 MetaspaceAux::print_on(st); 3459 } 3460 3461 void G1CollectedHeap::print_extended_on(outputStream* st) const { 3462 print_on(st); 3463 3464 // Print the per-region information. 3465 st->cr(); 3466 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), " 3467 "HS=humongous(starts), HC=humongous(continues), " 3468 "CS=collection set, F=free, TS=gc time stamp, " 3469 "PTAMS=previous top-at-mark-start, " 3470 "NTAMS=next top-at-mark-start)"); 3471 PrintRegionClosure blk(st); 3472 heap_region_iterate(&blk); 3473 } 3474 3475 void G1CollectedHeap::print_on_error(outputStream* st) const { 3476 this->CollectedHeap::print_on_error(st); 3477 3478 if (_cm != NULL) { 3479 st->cr(); 3480 _cm->print_on_error(st); 3481 } 3482 } 3483 3484 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 3485 if (G1CollectedHeap::use_parallel_gc_threads()) { 3486 workers()->print_worker_threads_on(st); 3487 } 3488 _cmThread->print_on(st); 3489 st->cr(); 3490 _cm->print_worker_threads_on(st); 3491 _cg1r->print_worker_threads_on(st); 3492 if (G1StringDedup::is_enabled()) { 3493 G1StringDedup::print_worker_threads_on(st); 3494 } 3495 } 3496 3497 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 3498 if (G1CollectedHeap::use_parallel_gc_threads()) { 3499 workers()->threads_do(tc); 3500 } 3501 tc->do_thread(_cmThread); 3502 _cg1r->threads_do(tc); 3503 if (G1StringDedup::is_enabled()) { 3504 G1StringDedup::threads_do(tc); 3505 } 3506 } 3507 3508 void G1CollectedHeap::print_tracing_info() const { 3509 // We'll overload this to mean "trace GC pause statistics." 3510 if (TraceGen0Time || TraceGen1Time) { 3511 // The "G1CollectorPolicy" is keeping track of these stats, so delegate 3512 // to that. 3513 g1_policy()->print_tracing_info(); 3514 } 3515 if (G1SummarizeRSetStats) { 3516 g1_rem_set()->print_summary_info(); 3517 } 3518 if (G1SummarizeConcMark) { 3519 concurrent_mark()->print_summary_info(); 3520 } 3521 g1_policy()->print_yg_surv_rate_info(); 3522 SpecializationStats::print(); 3523 } 3524 3525 #ifndef PRODUCT 3526 // Helpful for debugging RSet issues. 3527 3528 class PrintRSetsClosure : public HeapRegionClosure { 3529 private: 3530 const char* _msg; 3531 size_t _occupied_sum; 3532 3533 public: 3534 bool doHeapRegion(HeapRegion* r) { 3535 HeapRegionRemSet* hrrs = r->rem_set(); 3536 size_t occupied = hrrs->occupied(); 3537 _occupied_sum += occupied; 3538 3539 gclog_or_tty->print_cr("Printing RSet for region " HR_FORMAT, 3540 HR_FORMAT_PARAMS(r)); 3541 if (occupied == 0) { 3542 gclog_or_tty->print_cr(" RSet is empty"); 3543 } else { 3544 hrrs->print(); 3545 } 3546 gclog_or_tty->print_cr("----------"); 3547 return false; 3548 } 3549 3550 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 3551 gclog_or_tty->cr(); 3552 gclog_or_tty->print_cr("========================================"); 3553 gclog_or_tty->print_cr("%s", msg); 3554 gclog_or_tty->cr(); 3555 } 3556 3557 ~PrintRSetsClosure() { 3558 gclog_or_tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum); 3559 gclog_or_tty->print_cr("========================================"); 3560 gclog_or_tty->cr(); 3561 } 3562 }; 3563 3564 void G1CollectedHeap::print_cset_rsets() { 3565 PrintRSetsClosure cl("Printing CSet RSets"); 3566 collection_set_iterate(&cl); 3567 } 3568 3569 void G1CollectedHeap::print_all_rsets() { 3570 PrintRSetsClosure cl("Printing All RSets");; 3571 heap_region_iterate(&cl); 3572 } 3573 #endif // PRODUCT 3574 3575 G1CollectedHeap* G1CollectedHeap::heap() { 3576 assert(_sh->kind() == CollectedHeap::G1CollectedHeap, 3577 "not a garbage-first heap"); 3578 return _g1h; 3579 } 3580 3581 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 3582 // always_do_update_barrier = false; 3583 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 3584 // Fill TLAB's and such 3585 accumulate_statistics_all_tlabs(); 3586 ensure_parsability(true); 3587 3588 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) && 3589 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) { 3590 g1_rem_set()->print_periodic_summary_info("Before GC RS summary"); 3591 } 3592 } 3593 3594 void G1CollectedHeap::gc_epilogue(bool full) { 3595 3596 if (G1SummarizeRSetStats && 3597 (G1SummarizeRSetStatsPeriod > 0) && 3598 // we are at the end of the GC. Total collections has already been increased. 3599 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) { 3600 g1_rem_set()->print_periodic_summary_info("After GC RS summary"); 3601 } 3602 3603 // FIXME: what is this about? 3604 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 3605 // is set. 3606 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(), 3607 "derived pointer present")); 3608 // always_do_update_barrier = true; 3609 3610 resize_all_tlabs(); 3611 allocation_context_stats().update(full); 3612 3613 // We have just completed a GC. Update the soft reference 3614 // policy with the new heap occupancy 3615 Universe::update_heap_info_at_gc(); 3616 } 3617 3618 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 3619 uint gc_count_before, 3620 bool* succeeded, 3621 GCCause::Cause gc_cause) { 3622 assert_heap_not_locked_and_not_at_safepoint(); 3623 g1_policy()->record_stop_world_start(); 3624 VM_G1IncCollectionPause op(gc_count_before, 3625 word_size, 3626 false, /* should_initiate_conc_mark */ 3627 g1_policy()->max_pause_time_ms(), 3628 gc_cause); 3629 3630 op.set_allocation_context(AllocationContext::current()); 3631 VMThread::execute(&op); 3632 3633 HeapWord* result = op.result(); 3634 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 3635 assert(result == NULL || ret_succeeded, 3636 "the result should be NULL if the VM did not succeed"); 3637 *succeeded = ret_succeeded; 3638 3639 assert_heap_not_locked(); 3640 return result; 3641 } 3642 3643 void 3644 G1CollectedHeap::doConcurrentMark() { 3645 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 3646 if (!_cmThread->in_progress()) { 3647 _cmThread->set_started(); 3648 CGC_lock->notify(); 3649 } 3650 } 3651 3652 size_t G1CollectedHeap::pending_card_num() { 3653 size_t extra_cards = 0; 3654 JavaThread *curr = Threads::first(); 3655 while (curr != NULL) { 3656 DirtyCardQueue& dcq = curr->dirty_card_queue(); 3657 extra_cards += dcq.size(); 3658 curr = curr->next(); 3659 } 3660 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 3661 size_t buffer_size = dcqs.buffer_size(); 3662 size_t buffer_num = dcqs.completed_buffers_num(); 3663 3664 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes 3665 // in bytes - not the number of 'entries'. We need to convert 3666 // into a number of cards. 3667 return (buffer_size * buffer_num + extra_cards) / oopSize; 3668 } 3669 3670 size_t G1CollectedHeap::cards_scanned() { 3671 return g1_rem_set()->cardsScanned(); 3672 } 3673 3674 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 3675 private: 3676 size_t _total_humongous; 3677 size_t _candidate_humongous; 3678 3679 DirtyCardQueue _dcq; 3680 3681 // We don't nominate objects with many remembered set entries, on 3682 // the assumption that such objects are likely still live. 3683 bool is_remset_small(HeapRegion* region) const { 3684 HeapRegionRemSet* const rset = region->rem_set(); 3685 return G1EagerReclaimHumongousObjectsWithStaleRefs 3686 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) 3687 : rset->is_empty(); 3688 } 3689 3690 bool is_typeArray_region(HeapRegion* region) const { 3691 return oop(region->bottom())->is_typeArray(); 3692 } 3693 3694 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const { 3695 assert(region->startsHumongous(), "Must start a humongous object"); 3696 3697 // Candidate selection must satisfy the following constraints 3698 // while concurrent marking is in progress: 3699 // 3700 // * In order to maintain SATB invariants, an object must not be 3701 // reclaimed if it was allocated before the start of marking and 3702 // has not had its references scanned. Such an object must have 3703 // its references (including type metadata) scanned to ensure no 3704 // live objects are missed by the marking process. Objects 3705 // allocated after the start of concurrent marking don't need to 3706 // be scanned. 3707 // 3708 // * An object must not be reclaimed if it is on the concurrent 3709 // mark stack. Objects allocated after the start of concurrent 3710 // marking are never pushed on the mark stack. 3711 // 3712 // Nominating only objects allocated after the start of concurrent 3713 // marking is sufficient to meet both constraints. This may miss 3714 // some objects that satisfy the constraints, but the marking data 3715 // structures don't support efficiently performing the needed 3716 // additional tests or scrubbing of the mark stack. 3717 // 3718 // However, we presently only nominate is_typeArray() objects. 3719 // A humongous object containing references induces remembered 3720 // set entries on other regions. In order to reclaim such an 3721 // object, those remembered sets would need to be cleaned up. 3722 // 3723 // We also treat is_typeArray() objects specially, allowing them 3724 // to be reclaimed even if allocated before the start of 3725 // concurrent mark. For this we rely on mark stack insertion to 3726 // exclude is_typeArray() objects, preventing reclaiming an object 3727 // that is in the mark stack. We also rely on the metadata for 3728 // such objects to be built-in and so ensured to be kept live. 3729 // Frequent allocation and drop of large binary blobs is an 3730 // important use case for eager reclaim, and this special handling 3731 // may reduce needed headroom. 3732 3733 return is_typeArray_region(region) && is_remset_small(region); 3734 } 3735 3736 public: 3737 RegisterHumongousWithInCSetFastTestClosure() 3738 : _total_humongous(0), 3739 _candidate_humongous(0), 3740 _dcq(&JavaThread::dirty_card_queue_set()) { 3741 } 3742 3743 virtual bool doHeapRegion(HeapRegion* r) { 3744 if (!r->startsHumongous()) { 3745 return false; 3746 } 3747 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 3748 3749 bool is_candidate = humongous_region_is_candidate(g1h, r); 3750 uint rindex = r->hrm_index(); 3751 g1h->set_humongous_reclaim_candidate(rindex, is_candidate); 3752 if (is_candidate) { 3753 _candidate_humongous++; 3754 g1h->register_humongous_region_with_in_cset_fast_test(rindex); 3755 // Is_candidate already filters out humongous object with large remembered sets. 3756 // If we have a humongous object with a few remembered sets, we simply flush these 3757 // remembered set entries into the DCQS. That will result in automatic 3758 // re-evaluation of their remembered set entries during the following evacuation 3759 // phase. 3760 if (!r->rem_set()->is_empty()) { 3761 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 3762 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 3763 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set(); 3764 HeapRegionRemSetIterator hrrs(r->rem_set()); 3765 size_t card_index; 3766 while (hrrs.has_next(card_index)) { 3767 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index); 3768 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 3769 *card_ptr = CardTableModRefBS::dirty_card_val(); 3770 _dcq.enqueue(card_ptr); 3771 } 3772 } 3773 assert(hrrs.n_yielded() == r->rem_set()->occupied(), 3774 err_msg("Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries", 3775 hrrs.n_yielded(), r->rem_set()->occupied())); 3776 r->rem_set()->clear_locked(); 3777 } 3778 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 3779 } 3780 _total_humongous++; 3781 3782 return false; 3783 } 3784 3785 size_t total_humongous() const { return _total_humongous; } 3786 size_t candidate_humongous() const { return _candidate_humongous; } 3787 3788 void flush_rem_set_entries() { _dcq.flush(); } 3789 }; 3790 3791 void G1CollectedHeap::register_humongous_regions_with_in_cset_fast_test() { 3792 if (!G1EagerReclaimHumongousObjects) { 3793 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0); 3794 return; 3795 } 3796 double time = os::elapsed_counter(); 3797 3798 // Collect reclaim candidate information and register candidates with cset. 3799 RegisterHumongousWithInCSetFastTestClosure cl; 3800 heap_region_iterate(&cl); 3801 3802 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0; 3803 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time, 3804 cl.total_humongous(), 3805 cl.candidate_humongous()); 3806 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 3807 3808 // Finally flush all remembered set entries to re-check into the global DCQS. 3809 cl.flush_rem_set_entries(); 3810 } 3811 3812 void 3813 G1CollectedHeap::setup_surviving_young_words() { 3814 assert(_surviving_young_words == NULL, "pre-condition"); 3815 uint array_length = g1_policy()->young_cset_region_length(); 3816 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC); 3817 if (_surviving_young_words == NULL) { 3818 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR, 3819 "Not enough space for young surv words summary."); 3820 } 3821 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t)); 3822 #ifdef ASSERT 3823 for (uint i = 0; i < array_length; ++i) { 3824 assert( _surviving_young_words[i] == 0, "memset above" ); 3825 } 3826 #endif // !ASSERT 3827 } 3828 3829 void 3830 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) { 3831 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3832 uint array_length = g1_policy()->young_cset_region_length(); 3833 for (uint i = 0; i < array_length; ++i) { 3834 _surviving_young_words[i] += surv_young_words[i]; 3835 } 3836 } 3837 3838 void 3839 G1CollectedHeap::cleanup_surviving_young_words() { 3840 guarantee( _surviving_young_words != NULL, "pre-condition" ); 3841 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC); 3842 _surviving_young_words = NULL; 3843 } 3844 3845 class VerifyRegionRemSetClosure : public HeapRegionClosure { 3846 public: 3847 bool doHeapRegion(HeapRegion* hr) { 3848 if (!hr->continuesHumongous()) { 3849 hr->verify_rem_set(); 3850 } 3851 return false; 3852 } 3853 }; 3854 3855 #ifdef ASSERT 3856 class VerifyCSetClosure: public HeapRegionClosure { 3857 public: 3858 bool doHeapRegion(HeapRegion* hr) { 3859 // Here we check that the CSet region's RSet is ready for parallel 3860 // iteration. The fields that we'll verify are only manipulated 3861 // when the region is part of a CSet and is collected. Afterwards, 3862 // we reset these fields when we clear the region's RSet (when the 3863 // region is freed) so they are ready when the region is 3864 // re-allocated. The only exception to this is if there's an 3865 // evacuation failure and instead of freeing the region we leave 3866 // it in the heap. In that case, we reset these fields during 3867 // evacuation failure handling. 3868 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification"); 3869 3870 // Here's a good place to add any other checks we'd like to 3871 // perform on CSet regions. 3872 return false; 3873 } 3874 }; 3875 #endif // ASSERT 3876 3877 #if TASKQUEUE_STATS 3878 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 3879 st->print_raw_cr("GC Task Stats"); 3880 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 3881 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 3882 } 3883 3884 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const { 3885 print_taskqueue_stats_hdr(st); 3886 3887 TaskQueueStats totals; 3888 const int n = workers() != NULL ? workers()->total_workers() : 1; 3889 for (int i = 0; i < n; ++i) { 3890 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr(); 3891 totals += task_queue(i)->stats; 3892 } 3893 st->print_raw("tot "); totals.print(st); st->cr(); 3894 3895 DEBUG_ONLY(totals.verify()); 3896 } 3897 3898 void G1CollectedHeap::reset_taskqueue_stats() { 3899 const int n = workers() != NULL ? workers()->total_workers() : 1; 3900 for (int i = 0; i < n; ++i) { 3901 task_queue(i)->stats.reset(); 3902 } 3903 } 3904 #endif // TASKQUEUE_STATS 3905 3906 void G1CollectedHeap::log_gc_header() { 3907 if (!G1Log::fine()) { 3908 return; 3909 } 3910 3911 gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id()); 3912 3913 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause()) 3914 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)") 3915 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : ""); 3916 3917 gclog_or_tty->print("[%s", (const char*)gc_cause_str); 3918 } 3919 3920 void G1CollectedHeap::log_gc_footer(double pause_time_sec) { 3921 if (!G1Log::fine()) { 3922 return; 3923 } 3924 3925 if (G1Log::finer()) { 3926 if (evacuation_failed()) { 3927 gclog_or_tty->print(" (to-space exhausted)"); 3928 } 3929 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3930 g1_policy()->phase_times()->note_gc_end(); 3931 g1_policy()->phase_times()->print(pause_time_sec); 3932 g1_policy()->print_detailed_heap_transition(); 3933 } else { 3934 if (evacuation_failed()) { 3935 gclog_or_tty->print("--"); 3936 } 3937 g1_policy()->print_heap_transition(); 3938 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3939 } 3940 gclog_or_tty->flush(); 3941 } 3942 3943 bool 3944 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3945 assert_at_safepoint(true /* should_be_vm_thread */); 3946 guarantee(!is_gc_active(), "collection is not reentrant"); 3947 3948 if (GC_locker::check_active_before_gc()) { 3949 return false; 3950 } 3951 3952 _gc_timer_stw->register_gc_start(); 3953 3954 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 3955 3956 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3957 ResourceMark rm; 3958 3959 print_heap_before_gc(); 3960 trace_heap_before_gc(_gc_tracer_stw); 3961 3962 verify_region_sets_optional(); 3963 verify_dirty_young_regions(); 3964 3965 // This call will decide whether this pause is an initial-mark 3966 // pause. If it is, during_initial_mark_pause() will return true 3967 // for the duration of this pause. 3968 g1_policy()->decide_on_conc_mark_initiation(); 3969 3970 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3971 assert(!g1_policy()->during_initial_mark_pause() || 3972 g1_policy()->gcs_are_young(), "sanity"); 3973 3974 // We also do not allow mixed GCs during marking. 3975 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity"); 3976 3977 // Record whether this pause is an initial mark. When the current 3978 // thread has completed its logging output and it's safe to signal 3979 // the CM thread, the flag's value in the policy has been reset. 3980 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause(); 3981 3982 // Inner scope for scope based logging, timers, and stats collection 3983 { 3984 EvacuationInfo evacuation_info; 3985 3986 if (g1_policy()->during_initial_mark_pause()) { 3987 // We are about to start a marking cycle, so we increment the 3988 // full collection counter. 3989 increment_old_marking_cycles_started(); 3990 register_concurrent_cycle_start(_gc_timer_stw->gc_start()); 3991 } 3992 3993 _gc_tracer_stw->report_yc_type(yc_type()); 3994 3995 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 3996 3997 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 3998 workers()->active_workers(), 3999 Threads::number_of_non_daemon_threads()); 4000 assert(UseDynamicNumberOfGCThreads || 4001 active_workers == workers()->total_workers(), 4002 "If not dynamic should be using all the workers"); 4003 workers()->set_active_workers(active_workers); 4004 4005 4006 double pause_start_sec = os::elapsedTime(); 4007 g1_policy()->phase_times()->note_gc_start(active_workers, mark_in_progress()); 4008 log_gc_header(); 4009 4010 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 4011 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause(), 4012 yc_type() == Mixed /* allMemoryPoolsAffected */); 4013 4014 // If the secondary_free_list is not empty, append it to the 4015 // free_list. No need to wait for the cleanup operation to finish; 4016 // the region allocation code will check the secondary_free_list 4017 // and wait if necessary. If the G1StressConcRegionFreeing flag is 4018 // set, skip this step so that the region allocation code has to 4019 // get entries from the secondary_free_list. 4020 if (!G1StressConcRegionFreeing) { 4021 append_secondary_free_list_if_not_empty_with_lock(); 4022 } 4023 4024 assert(check_young_list_well_formed(), "young list should be well formed"); 4025 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue), 4026 "sanity check"); 4027 4028 // Don't dynamically change the number of GC threads this early. A value of 4029 // 0 is used to indicate serial work. When parallel work is done, 4030 // it will be set. 4031 4032 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 4033 IsGCActiveMark x; 4034 4035 gc_prologue(false); 4036 increment_total_collections(false /* full gc */); 4037 increment_gc_time_stamp(); 4038 4039 if (VerifyRememberedSets) { 4040 if (!VerifySilently) { 4041 gclog_or_tty->print_cr("[Verifying RemSets before GC]"); 4042 } 4043 VerifyRegionRemSetClosure v_cl; 4044 heap_region_iterate(&v_cl); 4045 } 4046 4047 verify_before_gc(); 4048 check_bitmaps("GC Start"); 4049 4050 COMPILER2_PRESENT(DerivedPointerTable::clear()); 4051 4052 // Please see comment in g1CollectedHeap.hpp and 4053 // G1CollectedHeap::ref_processing_init() to see how 4054 // reference processing currently works in G1. 4055 4056 // Enable discovery in the STW reference processor 4057 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, 4058 true /*verify_no_refs*/); 4059 4060 { 4061 // We want to temporarily turn off discovery by the 4062 // CM ref processor, if necessary, and turn it back on 4063 // on again later if we do. Using a scoped 4064 // NoRefDiscovery object will do this. 4065 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 4066 4067 // Forget the current alloc region (we might even choose it to be part 4068 // of the collection set!). 4069 _allocator->release_mutator_alloc_region(); 4070 4071 // We should call this after we retire the mutator alloc 4072 // region(s) so that all the ALLOC / RETIRE events are generated 4073 // before the start GC event. 4074 _hr_printer.start_gc(false /* full */, (size_t) total_collections()); 4075 4076 // This timing is only used by the ergonomics to handle our pause target. 4077 // It is unclear why this should not include the full pause. We will 4078 // investigate this in CR 7178365. 4079 // 4080 // Preserving the old comment here if that helps the investigation: 4081 // 4082 // The elapsed time induced by the start time below deliberately elides 4083 // the possible verification above. 4084 double sample_start_time_sec = os::elapsedTime(); 4085 4086 #if YOUNG_LIST_VERBOSE 4087 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:"); 4088 _young_list->print(); 4089 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 4090 #endif // YOUNG_LIST_VERBOSE 4091 4092 g1_policy()->record_collection_pause_start(sample_start_time_sec, *_gc_tracer_stw); 4093 4094 double scan_wait_start = os::elapsedTime(); 4095 // We have to wait until the CM threads finish scanning the 4096 // root regions as it's the only way to ensure that all the 4097 // objects on them have been correctly scanned before we start 4098 // moving them during the GC. 4099 bool waited = _cm->root_regions()->wait_until_scan_finished(); 4100 double wait_time_ms = 0.0; 4101 if (waited) { 4102 double scan_wait_end = os::elapsedTime(); 4103 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 4104 } 4105 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 4106 4107 #if YOUNG_LIST_VERBOSE 4108 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:"); 4109 _young_list->print(); 4110 #endif // YOUNG_LIST_VERBOSE 4111 4112 if (g1_policy()->during_initial_mark_pause()) { 4113 concurrent_mark()->checkpointRootsInitialPre(); 4114 } 4115 4116 #if YOUNG_LIST_VERBOSE 4117 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:"); 4118 _young_list->print(); 4119 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 4120 #endif // YOUNG_LIST_VERBOSE 4121 4122 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info); 4123 4124 // Make sure the remembered sets are up to date. This needs to be 4125 // done before register_humongous_regions_with_cset(), because the 4126 // remembered sets are used there to choose eager reclaim candidates. 4127 // If the remembered sets are not up to date we might miss some 4128 // entries that need to be handled. 4129 g1_rem_set()->cleanupHRRS(); 4130 4131 register_humongous_regions_with_in_cset_fast_test(); 4132 4133 assert(check_cset_fast_test(), "Inconsistency in the InCSetState table."); 4134 4135 _cm->note_start_of_gc(); 4136 // We call this after finalize_cset() to 4137 // ensure that the CSet has been finalized. 4138 _cm->verify_no_cset_oops(); 4139 4140 if (_hr_printer.is_active()) { 4141 HeapRegion* hr = g1_policy()->collection_set(); 4142 while (hr != NULL) { 4143 _hr_printer.cset(hr); 4144 hr = hr->next_in_collection_set(); 4145 } 4146 } 4147 4148 #ifdef ASSERT 4149 VerifyCSetClosure cl; 4150 collection_set_iterate(&cl); 4151 #endif // ASSERT 4152 4153 setup_surviving_young_words(); 4154 4155 // Initialize the GC alloc regions. 4156 _allocator->init_gc_alloc_regions(evacuation_info); 4157 4158 // Actually do the work... 4159 evacuate_collection_set(evacuation_info); 4160 4161 free_collection_set(g1_policy()->collection_set(), evacuation_info); 4162 4163 eagerly_reclaim_humongous_regions(); 4164 4165 g1_policy()->clear_collection_set(); 4166 4167 cleanup_surviving_young_words(); 4168 4169 // Start a new incremental collection set for the next pause. 4170 g1_policy()->start_incremental_cset_building(); 4171 4172 clear_cset_fast_test(); 4173 4174 _young_list->reset_sampled_info(); 4175 4176 // Don't check the whole heap at this point as the 4177 // GC alloc regions from this pause have been tagged 4178 // as survivors and moved on to the survivor list. 4179 // Survivor regions will fail the !is_young() check. 4180 assert(check_young_list_empty(false /* check_heap */), 4181 "young list should be empty"); 4182 4183 #if YOUNG_LIST_VERBOSE 4184 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:"); 4185 _young_list->print(); 4186 #endif // YOUNG_LIST_VERBOSE 4187 4188 g1_policy()->record_survivor_regions(_young_list->survivor_length(), 4189 _young_list->first_survivor_region(), 4190 _young_list->last_survivor_region()); 4191 4192 _young_list->reset_auxilary_lists(); 4193 4194 if (evacuation_failed()) { 4195 _allocator->set_used(recalculate_used()); 4196 uint n_queues = MAX2((int)ParallelGCThreads, 1); 4197 for (uint i = 0; i < n_queues; i++) { 4198 if (_evacuation_failed_info_array[i].has_failed()) { 4199 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 4200 } 4201 } 4202 } else { 4203 // The "used" of the the collection set have already been subtracted 4204 // when they were freed. Add in the bytes evacuated. 4205 _allocator->increase_used(g1_policy()->bytes_copied_during_gc()); 4206 } 4207 4208 if (g1_policy()->during_initial_mark_pause()) { 4209 // We have to do this before we notify the CM threads that 4210 // they can start working to make sure that all the 4211 // appropriate initialization is done on the CM object. 4212 concurrent_mark()->checkpointRootsInitialPost(); 4213 set_marking_started(); 4214 // Note that we don't actually trigger the CM thread at 4215 // this point. We do that later when we're sure that 4216 // the current thread has completed its logging output. 4217 } 4218 4219 allocate_dummy_regions(); 4220 4221 #if YOUNG_LIST_VERBOSE 4222 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:"); 4223 _young_list->print(); 4224 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 4225 #endif // YOUNG_LIST_VERBOSE 4226 4227 _allocator->init_mutator_alloc_region(); 4228 4229 { 4230 size_t expand_bytes = g1_policy()->expansion_amount(); 4231 if (expand_bytes > 0) { 4232 size_t bytes_before = capacity(); 4233 // No need for an ergo verbose message here, 4234 // expansion_amount() does this when it returns a value > 0. 4235 if (!expand(expand_bytes)) { 4236 // We failed to expand the heap. Cannot do anything about it. 4237 } 4238 } 4239 } 4240 4241 // We redo the verification but now wrt to the new CSet which 4242 // has just got initialized after the previous CSet was freed. 4243 _cm->verify_no_cset_oops(); 4244 _cm->note_end_of_gc(); 4245 4246 // This timing is only used by the ergonomics to handle our pause target. 4247 // It is unclear why this should not include the full pause. We will 4248 // investigate this in CR 7178365. 4249 double sample_end_time_sec = os::elapsedTime(); 4250 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 4251 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info); 4252 4253 MemoryService::track_memory_usage(); 4254 4255 // In prepare_for_verify() below we'll need to scan the deferred 4256 // update buffers to bring the RSets up-to-date if 4257 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 4258 // the update buffers we'll probably need to scan cards on the 4259 // regions we just allocated to (i.e., the GC alloc 4260 // regions). However, during the last GC we called 4261 // set_saved_mark() on all the GC alloc regions, so card 4262 // scanning might skip the [saved_mark_word()...top()] area of 4263 // those regions (i.e., the area we allocated objects into 4264 // during the last GC). But it shouldn't. Given that 4265 // saved_mark_word() is conditional on whether the GC time stamp 4266 // on the region is current or not, by incrementing the GC time 4267 // stamp here we invalidate all the GC time stamps on all the 4268 // regions and saved_mark_word() will simply return top() for 4269 // all the regions. This is a nicer way of ensuring this rather 4270 // than iterating over the regions and fixing them. In fact, the 4271 // GC time stamp increment here also ensures that 4272 // saved_mark_word() will return top() between pauses, i.e., 4273 // during concurrent refinement. So we don't need the 4274 // is_gc_active() check to decided which top to use when 4275 // scanning cards (see CR 7039627). 4276 increment_gc_time_stamp(); 4277 4278 if (VerifyRememberedSets) { 4279 if (!VerifySilently) { 4280 gclog_or_tty->print_cr("[Verifying RemSets after GC]"); 4281 } 4282 VerifyRegionRemSetClosure v_cl; 4283 heap_region_iterate(&v_cl); 4284 } 4285 4286 verify_after_gc(); 4287 check_bitmaps("GC End"); 4288 4289 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 4290 ref_processor_stw()->verify_no_references_recorded(); 4291 4292 // CM reference discovery will be re-enabled if necessary. 4293 } 4294 4295 // We should do this after we potentially expand the heap so 4296 // that all the COMMIT events are generated before the end GC 4297 // event, and after we retire the GC alloc regions so that all 4298 // RETIRE events are generated before the end GC event. 4299 _hr_printer.end_gc(false /* full */, (size_t) total_collections()); 4300 4301 #ifdef TRACESPINNING 4302 ParallelTaskTerminator::print_termination_counts(); 4303 #endif 4304 4305 gc_epilogue(false); 4306 } 4307 4308 // Print the remainder of the GC log output. 4309 log_gc_footer(os::elapsedTime() - pause_start_sec); 4310 4311 // It is not yet to safe to tell the concurrent mark to 4312 // start as we have some optional output below. We don't want the 4313 // output from the concurrent mark thread interfering with this 4314 // logging output either. 4315 4316 _hrm.verify_optional(); 4317 verify_region_sets_optional(); 4318 4319 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats()); 4320 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 4321 4322 print_heap_after_gc(); 4323 trace_heap_after_gc(_gc_tracer_stw); 4324 4325 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 4326 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 4327 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 4328 // before any GC notifications are raised. 4329 g1mm()->update_sizes(); 4330 4331 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 4332 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 4333 _gc_timer_stw->register_gc_end(); 4334 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 4335 } 4336 // It should now be safe to tell the concurrent mark thread to start 4337 // without its logging output interfering with the logging output 4338 // that came from the pause. 4339 4340 if (should_start_conc_mark) { 4341 // CAUTION: after the doConcurrentMark() call below, 4342 // the concurrent marking thread(s) could be running 4343 // concurrently with us. Make sure that anything after 4344 // this point does not assume that we are the only GC thread 4345 // running. Note: of course, the actual marking work will 4346 // not start until the safepoint itself is released in 4347 // SuspendibleThreadSet::desynchronize(). 4348 doConcurrentMark(); 4349 } 4350 4351 return true; 4352 } 4353 4354 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) { 4355 _drain_in_progress = false; 4356 set_evac_failure_closure(cl); 4357 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true); 4358 } 4359 4360 void G1CollectedHeap::finalize_for_evac_failure() { 4361 assert(_evac_failure_scan_stack != NULL && 4362 _evac_failure_scan_stack->length() == 0, 4363 "Postcondition"); 4364 assert(!_drain_in_progress, "Postcondition"); 4365 delete _evac_failure_scan_stack; 4366 _evac_failure_scan_stack = NULL; 4367 } 4368 4369 void G1CollectedHeap::remove_self_forwarding_pointers() { 4370 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity"); 4371 4372 double remove_self_forwards_start = os::elapsedTime(); 4373 4374 G1ParRemoveSelfForwardPtrsTask rsfp_task(this); 4375 4376 if (G1CollectedHeap::use_parallel_gc_threads()) { 4377 set_par_threads(); 4378 workers()->run_task(&rsfp_task); 4379 set_par_threads(0); 4380 } else { 4381 rsfp_task.work(0); 4382 } 4383 4384 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity"); 4385 4386 // Reset the claim values in the regions in the collection set. 4387 reset_cset_heap_region_claim_values(); 4388 4389 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity"); 4390 4391 // Now restore saved marks, if any. 4392 assert(_objs_with_preserved_marks.size() == 4393 _preserved_marks_of_objs.size(), "Both or none."); 4394 while (!_objs_with_preserved_marks.is_empty()) { 4395 oop obj = _objs_with_preserved_marks.pop(); 4396 markOop m = _preserved_marks_of_objs.pop(); 4397 obj->set_mark(m); 4398 } 4399 _objs_with_preserved_marks.clear(true); 4400 _preserved_marks_of_objs.clear(true); 4401 4402 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 4403 } 4404 4405 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) { 4406 _evac_failure_scan_stack->push(obj); 4407 } 4408 4409 void G1CollectedHeap::drain_evac_failure_scan_stack() { 4410 assert(_evac_failure_scan_stack != NULL, "precondition"); 4411 4412 while (_evac_failure_scan_stack->length() > 0) { 4413 oop obj = _evac_failure_scan_stack->pop(); 4414 _evac_failure_closure->set_region(heap_region_containing(obj)); 4415 obj->oop_iterate_backwards(_evac_failure_closure); 4416 } 4417 } 4418 4419 oop 4420 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, 4421 oop old) { 4422 assert(obj_in_cs(old), 4423 err_msg("obj: " PTR_FORMAT " should still be in the CSet", 4424 (HeapWord*) old)); 4425 markOop m = old->mark(); 4426 oop forward_ptr = old->forward_to_atomic(old); 4427 if (forward_ptr == NULL) { 4428 // Forward-to-self succeeded. 4429 assert(_par_scan_state != NULL, "par scan state"); 4430 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure(); 4431 uint queue_num = _par_scan_state->queue_num(); 4432 4433 _evacuation_failed = true; 4434 _evacuation_failed_info_array[queue_num].register_copy_failure(old->size()); 4435 if (_evac_failure_closure != cl) { 4436 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag); 4437 assert(!_drain_in_progress, 4438 "Should only be true while someone holds the lock."); 4439 // Set the global evac-failure closure to the current thread's. 4440 assert(_evac_failure_closure == NULL, "Or locking has failed."); 4441 set_evac_failure_closure(cl); 4442 // Now do the common part. 4443 handle_evacuation_failure_common(old, m); 4444 // Reset to NULL. 4445 set_evac_failure_closure(NULL); 4446 } else { 4447 // The lock is already held, and this is recursive. 4448 assert(_drain_in_progress, "This should only be the recursive case."); 4449 handle_evacuation_failure_common(old, m); 4450 } 4451 return old; 4452 } else { 4453 // Forward-to-self failed. Either someone else managed to allocate 4454 // space for this object (old != forward_ptr) or they beat us in 4455 // self-forwarding it (old == forward_ptr). 4456 assert(old == forward_ptr || !obj_in_cs(forward_ptr), 4457 err_msg("obj: " PTR_FORMAT " forwarded to: " PTR_FORMAT " " 4458 "should not be in the CSet", 4459 (HeapWord*) old, (HeapWord*) forward_ptr)); 4460 return forward_ptr; 4461 } 4462 } 4463 4464 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) { 4465 preserve_mark_if_necessary(old, m); 4466 4467 HeapRegion* r = heap_region_containing(old); 4468 if (!r->evacuation_failed()) { 4469 r->set_evacuation_failed(true); 4470 _hr_printer.evac_failure(r); 4471 } 4472 4473 push_on_evac_failure_scan_stack(old); 4474 4475 if (!_drain_in_progress) { 4476 // prevent recursion in copy_to_survivor_space() 4477 _drain_in_progress = true; 4478 drain_evac_failure_scan_stack(); 4479 _drain_in_progress = false; 4480 } 4481 } 4482 4483 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) { 4484 assert(evacuation_failed(), "Oversaving!"); 4485 // We want to call the "for_promotion_failure" version only in the 4486 // case of a promotion failure. 4487 if (m->must_be_preserved_for_promotion_failure(obj)) { 4488 _objs_with_preserved_marks.push(obj); 4489 _preserved_marks_of_objs.push(m); 4490 } 4491 } 4492 4493 void G1ParCopyHelper::mark_object(oop obj) { 4494 assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet"); 4495 4496 // We know that the object is not moving so it's safe to read its size. 4497 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id); 4498 } 4499 4500 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) { 4501 assert(from_obj->is_forwarded(), "from obj should be forwarded"); 4502 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee"); 4503 assert(from_obj != to_obj, "should not be self-forwarded"); 4504 4505 assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet"); 4506 assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet"); 4507 4508 // The object might be in the process of being copied by another 4509 // worker so we cannot trust that its to-space image is 4510 // well-formed. So we have to read its size from its from-space 4511 // image which we know should not be changing. 4512 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id); 4513 } 4514 4515 template <class T> 4516 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) { 4517 if (_g1->heap_region_containing_raw(new_obj)->is_young()) { 4518 _scanned_klass->record_modified_oops(); 4519 } 4520 } 4521 4522 template <G1Barrier barrier, G1Mark do_mark_object> 4523 template <class T> 4524 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) { 4525 T heap_oop = oopDesc::load_heap_oop(p); 4526 4527 if (oopDesc::is_null(heap_oop)) { 4528 return; 4529 } 4530 4531 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 4532 4533 assert(_worker_id == _par_scan_state->queue_num(), "sanity"); 4534 4535 const InCSetState state = _g1->in_cset_state(obj); 4536 if (state.is_in_cset()) { 4537 oop forwardee; 4538 markOop m = obj->mark(); 4539 if (m->is_marked()) { 4540 forwardee = (oop) m->decode_pointer(); 4541 } else { 4542 forwardee = _par_scan_state->copy_to_survivor_space(state, obj, m); 4543 } 4544 assert(forwardee != NULL, "forwardee should not be NULL"); 4545 oopDesc::encode_store_heap_oop(p, forwardee); 4546 if (do_mark_object != G1MarkNone && forwardee != obj) { 4547 // If the object is self-forwarded we don't need to explicitly 4548 // mark it, the evacuation failure protocol will do so. 4549 mark_forwarded_object(obj, forwardee); 4550 } 4551 4552 if (barrier == G1BarrierKlass) { 4553 do_klass_barrier(p, forwardee); 4554 } 4555 } else { 4556 if (state.is_humongous()) { 4557 _g1->set_humongous_is_live(obj); 4558 } 4559 // The object is not in collection set. If we're a root scanning 4560 // closure during an initial mark pause then attempt to mark the object. 4561 if (do_mark_object == G1MarkFromRoot) { 4562 mark_object(obj); 4563 } 4564 } 4565 4566 if (barrier == G1BarrierEvac) { 4567 _par_scan_state->update_rs(_from, p, _worker_id); 4568 } 4569 } 4570 4571 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p); 4572 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p); 4573 4574 class G1ParEvacuateFollowersClosure : public VoidClosure { 4575 protected: 4576 G1CollectedHeap* _g1h; 4577 G1ParScanThreadState* _par_scan_state; 4578 RefToScanQueueSet* _queues; 4579 ParallelTaskTerminator* _terminator; 4580 4581 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4582 RefToScanQueueSet* queues() { return _queues; } 4583 ParallelTaskTerminator* terminator() { return _terminator; } 4584 4585 public: 4586 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, 4587 G1ParScanThreadState* par_scan_state, 4588 RefToScanQueueSet* queues, 4589 ParallelTaskTerminator* terminator) 4590 : _g1h(g1h), _par_scan_state(par_scan_state), 4591 _queues(queues), _terminator(terminator) {} 4592 4593 void do_void(); 4594 4595 private: 4596 inline bool offer_termination(); 4597 }; 4598 4599 bool G1ParEvacuateFollowersClosure::offer_termination() { 4600 G1ParScanThreadState* const pss = par_scan_state(); 4601 pss->start_term_time(); 4602 const bool res = terminator()->offer_termination(); 4603 pss->end_term_time(); 4604 return res; 4605 } 4606 4607 void G1ParEvacuateFollowersClosure::do_void() { 4608 G1ParScanThreadState* const pss = par_scan_state(); 4609 pss->trim_queue(); 4610 do { 4611 pss->steal_and_trim_queue(queues()); 4612 } while (!offer_termination()); 4613 } 4614 4615 class G1KlassScanClosure : public KlassClosure { 4616 G1ParCopyHelper* _closure; 4617 bool _process_only_dirty; 4618 int _count; 4619 public: 4620 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty) 4621 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {} 4622 void do_klass(Klass* klass) { 4623 // If the klass has not been dirtied we know that there's 4624 // no references into the young gen and we can skip it. 4625 if (!_process_only_dirty || klass->has_modified_oops()) { 4626 // Clean the klass since we're going to scavenge all the metadata. 4627 klass->clear_modified_oops(); 4628 4629 // Tell the closure that this klass is the Klass to scavenge 4630 // and is the one to dirty if oops are left pointing into the young gen. 4631 _closure->set_scanned_klass(klass); 4632 4633 klass->oops_do(_closure); 4634 4635 _closure->set_scanned_klass(NULL); 4636 } 4637 _count++; 4638 } 4639 }; 4640 4641 class G1ParTask : public AbstractGangTask { 4642 protected: 4643 G1CollectedHeap* _g1h; 4644 RefToScanQueueSet *_queues; 4645 G1RootProcessor* _root_processor; 4646 ParallelTaskTerminator _terminator; 4647 uint _n_workers; 4648 4649 Mutex _stats_lock; 4650 Mutex* stats_lock() { return &_stats_lock; } 4651 4652 public: 4653 G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor) 4654 : AbstractGangTask("G1 collection"), 4655 _g1h(g1h), 4656 _queues(task_queues), 4657 _root_processor(root_processor), 4658 _terminator(0, _queues), 4659 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true) 4660 {} 4661 4662 RefToScanQueueSet* queues() { return _queues; } 4663 4664 RefToScanQueue *work_queue(int i) { 4665 return queues()->queue(i); 4666 } 4667 4668 ParallelTaskTerminator* terminator() { return &_terminator; } 4669 4670 virtual void set_for_termination(int active_workers) { 4671 _root_processor->set_num_workers(active_workers); 4672 terminator()->reset_for_reuse(active_workers); 4673 _n_workers = active_workers; 4674 } 4675 4676 // Helps out with CLD processing. 4677 // 4678 // During InitialMark we need to: 4679 // 1) Scavenge all CLDs for the young GC. 4680 // 2) Mark all objects directly reachable from strong CLDs. 4681 template <G1Mark do_mark_object> 4682 class G1CLDClosure : public CLDClosure { 4683 G1ParCopyClosure<G1BarrierNone, do_mark_object>* _oop_closure; 4684 G1ParCopyClosure<G1BarrierKlass, do_mark_object> _oop_in_klass_closure; 4685 G1KlassScanClosure _klass_in_cld_closure; 4686 bool _claim; 4687 4688 public: 4689 G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure, 4690 bool only_young, bool claim) 4691 : _oop_closure(oop_closure), 4692 _oop_in_klass_closure(oop_closure->g1(), 4693 oop_closure->pss(), 4694 oop_closure->rp()), 4695 _klass_in_cld_closure(&_oop_in_klass_closure, only_young), 4696 _claim(claim) { 4697 4698 } 4699 4700 void do_cld(ClassLoaderData* cld) { 4701 cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim); 4702 } 4703 }; 4704 4705 void work(uint worker_id) { 4706 if (worker_id >= _n_workers) return; // no work needed this round 4707 4708 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, os::elapsedTime()); 4709 4710 { 4711 ResourceMark rm; 4712 HandleMark hm; 4713 4714 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 4715 4716 G1ParScanThreadState pss(_g1h, worker_id, rp); 4717 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp); 4718 4719 pss.set_evac_failure_closure(&evac_failure_cl); 4720 4721 bool only_young = _g1h->g1_policy()->gcs_are_young(); 4722 4723 // Non-IM young GC. 4724 G1ParCopyClosure<G1BarrierNone, G1MarkNone> scan_only_root_cl(_g1h, &pss, rp); 4725 G1CLDClosure<G1MarkNone> scan_only_cld_cl(&scan_only_root_cl, 4726 only_young, // Only process dirty klasses. 4727 false); // No need to claim CLDs. 4728 // IM young GC. 4729 // Strong roots closures. 4730 G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot> scan_mark_root_cl(_g1h, &pss, rp); 4731 G1CLDClosure<G1MarkFromRoot> scan_mark_cld_cl(&scan_mark_root_cl, 4732 false, // Process all klasses. 4733 true); // Need to claim CLDs. 4734 // Weak roots closures. 4735 G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp); 4736 G1CLDClosure<G1MarkPromotedFromRoot> scan_mark_weak_cld_cl(&scan_mark_weak_root_cl, 4737 false, // Process all klasses. 4738 true); // Need to claim CLDs. 4739 4740 OopClosure* strong_root_cl; 4741 OopClosure* weak_root_cl; 4742 CLDClosure* strong_cld_cl; 4743 CLDClosure* weak_cld_cl; 4744 4745 bool trace_metadata = false; 4746 4747 if (_g1h->g1_policy()->during_initial_mark_pause()) { 4748 // We also need to mark copied objects. 4749 strong_root_cl = &scan_mark_root_cl; 4750 strong_cld_cl = &scan_mark_cld_cl; 4751 if (ClassUnloadingWithConcurrentMark) { 4752 weak_root_cl = &scan_mark_weak_root_cl; 4753 weak_cld_cl = &scan_mark_weak_cld_cl; 4754 trace_metadata = true; 4755 } else { 4756 weak_root_cl = &scan_mark_root_cl; 4757 weak_cld_cl = &scan_mark_cld_cl; 4758 } 4759 } else { 4760 strong_root_cl = &scan_only_root_cl; 4761 weak_root_cl = &scan_only_root_cl; 4762 strong_cld_cl = &scan_only_cld_cl; 4763 weak_cld_cl = &scan_only_cld_cl; 4764 } 4765 4766 pss.start_strong_roots(); 4767 4768 _root_processor->evacuate_roots(strong_root_cl, 4769 weak_root_cl, 4770 strong_cld_cl, 4771 weak_cld_cl, 4772 trace_metadata, 4773 worker_id); 4774 4775 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss); 4776 _root_processor->scan_remembered_sets(&push_heap_rs_cl, 4777 weak_root_cl, 4778 worker_id); 4779 pss.end_strong_roots(); 4780 4781 { 4782 double start = os::elapsedTime(); 4783 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator); 4784 evac.do_void(); 4785 double elapsed_sec = os::elapsedTime() - start; 4786 double term_sec = pss.term_time(); 4787 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec); 4788 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec); 4789 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, pss.term_attempts()); 4790 } 4791 _g1h->g1_policy()->record_thread_age_table(pss.age_table()); 4792 _g1h->update_surviving_young_words(pss.surviving_young_words()+1); 4793 4794 if (ParallelGCVerbose) { 4795 MutexLocker x(stats_lock()); 4796 pss.print_termination_stats(worker_id); 4797 } 4798 4799 assert(pss.queue_is_empty(), "should be empty"); 4800 4801 // Close the inner scope so that the ResourceMark and HandleMark 4802 // destructors are executed here and are included as part of the 4803 // "GC Worker Time". 4804 } 4805 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime()); 4806 } 4807 }; 4808 4809 class G1StringSymbolTableUnlinkTask : public AbstractGangTask { 4810 private: 4811 BoolObjectClosure* _is_alive; 4812 int _initial_string_table_size; 4813 int _initial_symbol_table_size; 4814 4815 bool _process_strings; 4816 int _strings_processed; 4817 int _strings_removed; 4818 4819 bool _process_symbols; 4820 int _symbols_processed; 4821 int _symbols_removed; 4822 4823 bool _do_in_parallel; 4824 public: 4825 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) : 4826 AbstractGangTask("String/Symbol Unlinking"), 4827 _is_alive(is_alive), 4828 _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()), 4829 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 4830 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) { 4831 4832 _initial_string_table_size = StringTable::the_table()->table_size(); 4833 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 4834 if (process_strings) { 4835 StringTable::clear_parallel_claimed_index(); 4836 } 4837 if (process_symbols) { 4838 SymbolTable::clear_parallel_claimed_index(); 4839 } 4840 } 4841 4842 ~G1StringSymbolTableUnlinkTask() { 4843 guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size, 4844 err_msg("claim value " INT32_FORMAT " after unlink less than initial string table size " INT32_FORMAT, 4845 StringTable::parallel_claimed_index(), _initial_string_table_size)); 4846 guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 4847 err_msg("claim value " INT32_FORMAT " after unlink less than initial symbol table size " INT32_FORMAT, 4848 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size)); 4849 4850 if (G1TraceStringSymbolTableScrubbing) { 4851 gclog_or_tty->print_cr("Cleaned string and symbol table, " 4852 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, " 4853 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed", 4854 strings_processed(), strings_removed(), 4855 symbols_processed(), symbols_removed()); 4856 } 4857 } 4858 4859 void work(uint worker_id) { 4860 if (_do_in_parallel) { 4861 int strings_processed = 0; 4862 int strings_removed = 0; 4863 int symbols_processed = 0; 4864 int symbols_removed = 0; 4865 if (_process_strings) { 4866 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 4867 Atomic::add(strings_processed, &_strings_processed); 4868 Atomic::add(strings_removed, &_strings_removed); 4869 } 4870 if (_process_symbols) { 4871 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 4872 Atomic::add(symbols_processed, &_symbols_processed); 4873 Atomic::add(symbols_removed, &_symbols_removed); 4874 } 4875 } else { 4876 if (_process_strings) { 4877 StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed); 4878 } 4879 if (_process_symbols) { 4880 SymbolTable::unlink(&_symbols_processed, &_symbols_removed); 4881 } 4882 } 4883 } 4884 4885 size_t strings_processed() const { return (size_t)_strings_processed; } 4886 size_t strings_removed() const { return (size_t)_strings_removed; } 4887 4888 size_t symbols_processed() const { return (size_t)_symbols_processed; } 4889 size_t symbols_removed() const { return (size_t)_symbols_removed; } 4890 }; 4891 4892 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 4893 private: 4894 static Monitor* _lock; 4895 4896 BoolObjectClosure* const _is_alive; 4897 const bool _unloading_occurred; 4898 const uint _num_workers; 4899 4900 // Variables used to claim nmethods. 4901 nmethod* _first_nmethod; 4902 volatile nmethod* _claimed_nmethod; 4903 4904 // The list of nmethods that need to be processed by the second pass. 4905 volatile nmethod* _postponed_list; 4906 volatile uint _num_entered_barrier; 4907 4908 public: 4909 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 4910 _is_alive(is_alive), 4911 _unloading_occurred(unloading_occurred), 4912 _num_workers(num_workers), 4913 _first_nmethod(NULL), 4914 _claimed_nmethod(NULL), 4915 _postponed_list(NULL), 4916 _num_entered_barrier(0) 4917 { 4918 nmethod::increase_unloading_clock(); 4919 _first_nmethod = CodeCache::alive_nmethod(CodeCache::first()); 4920 _claimed_nmethod = (volatile nmethod*)_first_nmethod; 4921 } 4922 4923 ~G1CodeCacheUnloadingTask() { 4924 CodeCache::verify_clean_inline_caches(); 4925 4926 CodeCache::set_needs_cache_clean(false); 4927 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 4928 4929 CodeCache::verify_icholder_relocations(); 4930 } 4931 4932 private: 4933 void add_to_postponed_list(nmethod* nm) { 4934 nmethod* old; 4935 do { 4936 old = (nmethod*)_postponed_list; 4937 nm->set_unloading_next(old); 4938 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old); 4939 } 4940 4941 void clean_nmethod(nmethod* nm) { 4942 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 4943 4944 if (postponed) { 4945 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 4946 add_to_postponed_list(nm); 4947 } 4948 4949 // Mark that this thread has been cleaned/unloaded. 4950 // After this call, it will be safe to ask if this nmethod was unloaded or not. 4951 nm->set_unloading_clock(nmethod::global_unloading_clock()); 4952 } 4953 4954 void clean_nmethod_postponed(nmethod* nm) { 4955 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 4956 } 4957 4958 static const int MaxClaimNmethods = 16; 4959 4960 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) { 4961 nmethod* first; 4962 nmethod* last; 4963 4964 do { 4965 *num_claimed_nmethods = 0; 4966 4967 first = last = (nmethod*)_claimed_nmethod; 4968 4969 if (first != NULL) { 4970 for (int i = 0; i < MaxClaimNmethods; i++) { 4971 last = CodeCache::alive_nmethod(CodeCache::next(last)); 4972 4973 if (last == NULL) { 4974 break; 4975 } 4976 4977 claimed_nmethods[i] = last; 4978 (*num_claimed_nmethods)++; 4979 } 4980 } 4981 4982 } while ((nmethod*)Atomic::cmpxchg_ptr(last, &_claimed_nmethod, first) != first); 4983 } 4984 4985 nmethod* claim_postponed_nmethod() { 4986 nmethod* claim; 4987 nmethod* next; 4988 4989 do { 4990 claim = (nmethod*)_postponed_list; 4991 if (claim == NULL) { 4992 return NULL; 4993 } 4994 4995 next = claim->unloading_next(); 4996 4997 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim); 4998 4999 return claim; 5000 } 5001 5002 public: 5003 // Mark that we're done with the first pass of nmethod cleaning. 5004 void barrier_mark(uint worker_id) { 5005 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 5006 _num_entered_barrier++; 5007 if (_num_entered_barrier == _num_workers) { 5008 ml.notify_all(); 5009 } 5010 } 5011 5012 // See if we have to wait for the other workers to 5013 // finish their first-pass nmethod cleaning work. 5014 void barrier_wait(uint worker_id) { 5015 if (_num_entered_barrier < _num_workers) { 5016 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 5017 while (_num_entered_barrier < _num_workers) { 5018 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 5019 } 5020 } 5021 } 5022 5023 // Cleaning and unloading of nmethods. Some work has to be postponed 5024 // to the second pass, when we know which nmethods survive. 5025 void work_first_pass(uint worker_id) { 5026 // The first nmethods is claimed by the first worker. 5027 if (worker_id == 0 && _first_nmethod != NULL) { 5028 clean_nmethod(_first_nmethod); 5029 _first_nmethod = NULL; 5030 } 5031 5032 int num_claimed_nmethods; 5033 nmethod* claimed_nmethods[MaxClaimNmethods]; 5034 5035 while (true) { 5036 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 5037 5038 if (num_claimed_nmethods == 0) { 5039 break; 5040 } 5041 5042 for (int i = 0; i < num_claimed_nmethods; i++) { 5043 clean_nmethod(claimed_nmethods[i]); 5044 } 5045 } 5046 5047 // The nmethod cleaning helps out and does the CodeCache part of MetadataOnStackMark. 5048 // Need to retire the buffers now that this thread has stopped cleaning nmethods. 5049 MetadataOnStackMark::retire_buffer_for_thread(Thread::current()); 5050 } 5051 5052 void work_second_pass(uint worker_id) { 5053 nmethod* nm; 5054 // Take care of postponed nmethods. 5055 while ((nm = claim_postponed_nmethod()) != NULL) { 5056 clean_nmethod_postponed(nm); 5057 } 5058 } 5059 }; 5060 5061 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock"); 5062 5063 class G1KlassCleaningTask : public StackObj { 5064 BoolObjectClosure* _is_alive; 5065 volatile jint _clean_klass_tree_claimed; 5066 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 5067 5068 public: 5069 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 5070 _is_alive(is_alive), 5071 _clean_klass_tree_claimed(0), 5072 _klass_iterator() { 5073 } 5074 5075 private: 5076 bool claim_clean_klass_tree_task() { 5077 if (_clean_klass_tree_claimed) { 5078 return false; 5079 } 5080 5081 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0; 5082 } 5083 5084 InstanceKlass* claim_next_klass() { 5085 Klass* klass; 5086 do { 5087 klass =_klass_iterator.next_klass(); 5088 } while (klass != NULL && !klass->oop_is_instance()); 5089 5090 return (InstanceKlass*)klass; 5091 } 5092 5093 public: 5094 5095 void clean_klass(InstanceKlass* ik) { 5096 ik->clean_weak_instanceklass_links(_is_alive); 5097 5098 if (JvmtiExport::has_redefined_a_class()) { 5099 InstanceKlass::purge_previous_versions(ik); 5100 } 5101 } 5102 5103 void work() { 5104 ResourceMark rm; 5105 5106 // One worker will clean the subklass/sibling klass tree. 5107 if (claim_clean_klass_tree_task()) { 5108 Klass::clean_subklass_tree(_is_alive); 5109 } 5110 5111 // All workers will help cleaning the classes, 5112 InstanceKlass* klass; 5113 while ((klass = claim_next_klass()) != NULL) { 5114 clean_klass(klass); 5115 } 5116 } 5117 }; 5118 5119 // To minimize the remark pause times, the tasks below are done in parallel. 5120 class G1ParallelCleaningTask : public AbstractGangTask { 5121 private: 5122 G1StringSymbolTableUnlinkTask _string_symbol_task; 5123 G1CodeCacheUnloadingTask _code_cache_task; 5124 G1KlassCleaningTask _klass_cleaning_task; 5125 5126 public: 5127 // The constructor is run in the VMThread. 5128 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) : 5129 AbstractGangTask("Parallel Cleaning"), 5130 _string_symbol_task(is_alive, process_strings, process_symbols), 5131 _code_cache_task(num_workers, is_alive, unloading_occurred), 5132 _klass_cleaning_task(is_alive) { 5133 } 5134 5135 void pre_work_verification() { 5136 // The VM Thread will have registered Metadata during the single-threaded phase of MetadataStackOnMark. 5137 assert(Thread::current()->is_VM_thread() 5138 || !MetadataOnStackMark::has_buffer_for_thread(Thread::current()), "Should be empty"); 5139 } 5140 5141 void post_work_verification() { 5142 assert(!MetadataOnStackMark::has_buffer_for_thread(Thread::current()), "Should be empty"); 5143 } 5144 5145 // The parallel work done by all worker threads. 5146 void work(uint worker_id) { 5147 pre_work_verification(); 5148 5149 // Do first pass of code cache cleaning. 5150 _code_cache_task.work_first_pass(worker_id); 5151 5152 // Let the threads mark that the first pass is done. 5153 _code_cache_task.barrier_mark(worker_id); 5154 5155 // Clean the Strings and Symbols. 5156 _string_symbol_task.work(worker_id); 5157 5158 // Wait for all workers to finish the first code cache cleaning pass. 5159 _code_cache_task.barrier_wait(worker_id); 5160 5161 // Do the second code cache cleaning work, which realize on 5162 // the liveness information gathered during the first pass. 5163 _code_cache_task.work_second_pass(worker_id); 5164 5165 // Clean all klasses that were not unloaded. 5166 _klass_cleaning_task.work(); 5167 5168 post_work_verification(); 5169 } 5170 }; 5171 5172 5173 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive, 5174 bool process_strings, 5175 bool process_symbols, 5176 bool class_unloading_occurred) { 5177 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 5178 workers()->active_workers() : 1); 5179 5180 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, 5181 n_workers, class_unloading_occurred); 5182 if (G1CollectedHeap::use_parallel_gc_threads()) { 5183 set_par_threads(n_workers); 5184 workers()->run_task(&g1_unlink_task); 5185 set_par_threads(0); 5186 } else { 5187 g1_unlink_task.work(0); 5188 } 5189 } 5190 5191 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive, 5192 bool process_strings, bool process_symbols) { 5193 { 5194 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 5195 _g1h->workers()->active_workers() : 1); 5196 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols); 5197 if (G1CollectedHeap::use_parallel_gc_threads()) { 5198 set_par_threads(n_workers); 5199 workers()->run_task(&g1_unlink_task); 5200 set_par_threads(0); 5201 } else { 5202 g1_unlink_task.work(0); 5203 } 5204 } 5205 5206 if (G1StringDedup::is_enabled()) { 5207 G1StringDedup::unlink(is_alive); 5208 } 5209 } 5210 5211 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 5212 private: 5213 DirtyCardQueueSet* _queue; 5214 public: 5215 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { } 5216 5217 virtual void work(uint worker_id) { 5218 G1GCPhaseTimes* phase_times = G1CollectedHeap::heap()->g1_policy()->phase_times(); 5219 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id); 5220 5221 RedirtyLoggedCardTableEntryClosure cl; 5222 if (G1CollectedHeap::heap()->use_parallel_gc_threads()) { 5223 _queue->par_apply_closure_to_all_completed_buffers(&cl); 5224 } else { 5225 _queue->apply_closure_to_all_completed_buffers(&cl); 5226 } 5227 5228 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_processed()); 5229 } 5230 }; 5231 5232 void G1CollectedHeap::redirty_logged_cards() { 5233 double redirty_logged_cards_start = os::elapsedTime(); 5234 5235 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 5236 _g1h->workers()->active_workers() : 1); 5237 5238 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set()); 5239 dirty_card_queue_set().reset_for_par_iteration(); 5240 if (use_parallel_gc_threads()) { 5241 set_par_threads(n_workers); 5242 workers()->run_task(&redirty_task); 5243 set_par_threads(0); 5244 } else { 5245 redirty_task.work(0); 5246 } 5247 5248 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 5249 dcq.merge_bufferlists(&dirty_card_queue_set()); 5250 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 5251 5252 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 5253 } 5254 5255 // Weak Reference Processing support 5256 5257 // An always "is_alive" closure that is used to preserve referents. 5258 // If the object is non-null then it's alive. Used in the preservation 5259 // of referent objects that are pointed to by reference objects 5260 // discovered by the CM ref processor. 5261 class G1AlwaysAliveClosure: public BoolObjectClosure { 5262 G1CollectedHeap* _g1; 5263 public: 5264 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 5265 bool do_object_b(oop p) { 5266 if (p != NULL) { 5267 return true; 5268 } 5269 return false; 5270 } 5271 }; 5272 5273 bool G1STWIsAliveClosure::do_object_b(oop p) { 5274 // An object is reachable if it is outside the collection set, 5275 // or is inside and copied. 5276 return !_g1->obj_in_cs(p) || p->is_forwarded(); 5277 } 5278 5279 // Non Copying Keep Alive closure 5280 class G1KeepAliveClosure: public OopClosure { 5281 G1CollectedHeap* _g1; 5282 public: 5283 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 5284 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 5285 void do_oop(oop* p) { 5286 oop obj = *p; 5287 assert(obj != NULL, "the caller should have filtered out NULL values"); 5288 5289 const InCSetState cset_state = _g1->in_cset_state(obj); 5290 if (!cset_state.is_in_cset_or_humongous()) { 5291 return; 5292 } 5293 if (cset_state.is_in_cset()) { 5294 assert( obj->is_forwarded(), "invariant" ); 5295 *p = obj->forwardee(); 5296 } else { 5297 assert(!obj->is_forwarded(), "invariant" ); 5298 assert(cset_state.is_humongous(), 5299 err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state.value())); 5300 _g1->set_humongous_is_live(obj); 5301 } 5302 } 5303 }; 5304 5305 // Copying Keep Alive closure - can be called from both 5306 // serial and parallel code as long as different worker 5307 // threads utilize different G1ParScanThreadState instances 5308 // and different queues. 5309 5310 class G1CopyingKeepAliveClosure: public OopClosure { 5311 G1CollectedHeap* _g1h; 5312 OopClosure* _copy_non_heap_obj_cl; 5313 G1ParScanThreadState* _par_scan_state; 5314 5315 public: 5316 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 5317 OopClosure* non_heap_obj_cl, 5318 G1ParScanThreadState* pss): 5319 _g1h(g1h), 5320 _copy_non_heap_obj_cl(non_heap_obj_cl), 5321 _par_scan_state(pss) 5322 {} 5323 5324 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 5325 virtual void do_oop( oop* p) { do_oop_work(p); } 5326 5327 template <class T> void do_oop_work(T* p) { 5328 oop obj = oopDesc::load_decode_heap_oop(p); 5329 5330 if (_g1h->is_in_cset_or_humongous(obj)) { 5331 // If the referent object has been forwarded (either copied 5332 // to a new location or to itself in the event of an 5333 // evacuation failure) then we need to update the reference 5334 // field and, if both reference and referent are in the G1 5335 // heap, update the RSet for the referent. 5336 // 5337 // If the referent has not been forwarded then we have to keep 5338 // it alive by policy. Therefore we have copy the referent. 5339 // 5340 // If the reference field is in the G1 heap then we can push 5341 // on the PSS queue. When the queue is drained (after each 5342 // phase of reference processing) the object and it's followers 5343 // will be copied, the reference field set to point to the 5344 // new location, and the RSet updated. Otherwise we need to 5345 // use the the non-heap or metadata closures directly to copy 5346 // the referent object and update the pointer, while avoiding 5347 // updating the RSet. 5348 5349 if (_g1h->is_in_g1_reserved(p)) { 5350 _par_scan_state->push_on_queue(p); 5351 } else { 5352 assert(!Metaspace::contains((const void*)p), 5353 err_msg("Unexpectedly found a pointer from metadata: " 5354 PTR_FORMAT, p)); 5355 _copy_non_heap_obj_cl->do_oop(p); 5356 } 5357 } 5358 } 5359 }; 5360 5361 // Serial drain queue closure. Called as the 'complete_gc' 5362 // closure for each discovered list in some of the 5363 // reference processing phases. 5364 5365 class G1STWDrainQueueClosure: public VoidClosure { 5366 protected: 5367 G1CollectedHeap* _g1h; 5368 G1ParScanThreadState* _par_scan_state; 5369 5370 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 5371 5372 public: 5373 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 5374 _g1h(g1h), 5375 _par_scan_state(pss) 5376 { } 5377 5378 void do_void() { 5379 G1ParScanThreadState* const pss = par_scan_state(); 5380 pss->trim_queue(); 5381 } 5382 }; 5383 5384 // Parallel Reference Processing closures 5385 5386 // Implementation of AbstractRefProcTaskExecutor for parallel reference 5387 // processing during G1 evacuation pauses. 5388 5389 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 5390 private: 5391 G1CollectedHeap* _g1h; 5392 RefToScanQueueSet* _queues; 5393 FlexibleWorkGang* _workers; 5394 int _active_workers; 5395 5396 public: 5397 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 5398 FlexibleWorkGang* workers, 5399 RefToScanQueueSet *task_queues, 5400 int n_workers) : 5401 _g1h(g1h), 5402 _queues(task_queues), 5403 _workers(workers), 5404 _active_workers(n_workers) 5405 { 5406 assert(n_workers > 0, "shouldn't call this otherwise"); 5407 } 5408 5409 // Executes the given task using concurrent marking worker threads. 5410 virtual void execute(ProcessTask& task); 5411 virtual void execute(EnqueueTask& task); 5412 }; 5413 5414 // Gang task for possibly parallel reference processing 5415 5416 class G1STWRefProcTaskProxy: public AbstractGangTask { 5417 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 5418 ProcessTask& _proc_task; 5419 G1CollectedHeap* _g1h; 5420 RefToScanQueueSet *_task_queues; 5421 ParallelTaskTerminator* _terminator; 5422 5423 public: 5424 G1STWRefProcTaskProxy(ProcessTask& proc_task, 5425 G1CollectedHeap* g1h, 5426 RefToScanQueueSet *task_queues, 5427 ParallelTaskTerminator* terminator) : 5428 AbstractGangTask("Process reference objects in parallel"), 5429 _proc_task(proc_task), 5430 _g1h(g1h), 5431 _task_queues(task_queues), 5432 _terminator(terminator) 5433 {} 5434 5435 virtual void work(uint worker_id) { 5436 // The reference processing task executed by a single worker. 5437 ResourceMark rm; 5438 HandleMark hm; 5439 5440 G1STWIsAliveClosure is_alive(_g1h); 5441 5442 G1ParScanThreadState pss(_g1h, worker_id, NULL); 5443 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL); 5444 5445 pss.set_evac_failure_closure(&evac_failure_cl); 5446 5447 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL); 5448 5449 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL); 5450 5451 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5452 5453 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5454 // We also need to mark copied objects. 5455 copy_non_heap_cl = ©_mark_non_heap_cl; 5456 } 5457 5458 // Keep alive closure. 5459 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss); 5460 5461 // Complete GC closure 5462 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator); 5463 5464 // Call the reference processing task's work routine. 5465 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 5466 5467 // Note we cannot assert that the refs array is empty here as not all 5468 // of the processing tasks (specifically phase2 - pp2_work) execute 5469 // the complete_gc closure (which ordinarily would drain the queue) so 5470 // the queue may not be empty. 5471 } 5472 }; 5473 5474 // Driver routine for parallel reference processing. 5475 // Creates an instance of the ref processing gang 5476 // task and has the worker threads execute it. 5477 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 5478 assert(_workers != NULL, "Need parallel worker threads."); 5479 5480 ParallelTaskTerminator terminator(_active_workers, _queues); 5481 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator); 5482 5483 _g1h->set_par_threads(_active_workers); 5484 _workers->run_task(&proc_task_proxy); 5485 _g1h->set_par_threads(0); 5486 } 5487 5488 // Gang task for parallel reference enqueueing. 5489 5490 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 5491 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 5492 EnqueueTask& _enq_task; 5493 5494 public: 5495 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 5496 AbstractGangTask("Enqueue reference objects in parallel"), 5497 _enq_task(enq_task) 5498 { } 5499 5500 virtual void work(uint worker_id) { 5501 _enq_task.work(worker_id); 5502 } 5503 }; 5504 5505 // Driver routine for parallel reference enqueueing. 5506 // Creates an instance of the ref enqueueing gang 5507 // task and has the worker threads execute it. 5508 5509 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 5510 assert(_workers != NULL, "Need parallel worker threads."); 5511 5512 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 5513 5514 _g1h->set_par_threads(_active_workers); 5515 _workers->run_task(&enq_task_proxy); 5516 _g1h->set_par_threads(0); 5517 } 5518 5519 // End of weak reference support closures 5520 5521 // Abstract task used to preserve (i.e. copy) any referent objects 5522 // that are in the collection set and are pointed to by reference 5523 // objects discovered by the CM ref processor. 5524 5525 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 5526 protected: 5527 G1CollectedHeap* _g1h; 5528 RefToScanQueueSet *_queues; 5529 ParallelTaskTerminator _terminator; 5530 uint _n_workers; 5531 5532 public: 5533 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) : 5534 AbstractGangTask("ParPreserveCMReferents"), 5535 _g1h(g1h), 5536 _queues(task_queues), 5537 _terminator(workers, _queues), 5538 _n_workers(workers) 5539 { } 5540 5541 void work(uint worker_id) { 5542 ResourceMark rm; 5543 HandleMark hm; 5544 5545 G1ParScanThreadState pss(_g1h, worker_id, NULL); 5546 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL); 5547 5548 pss.set_evac_failure_closure(&evac_failure_cl); 5549 5550 assert(pss.queue_is_empty(), "both queue and overflow should be empty"); 5551 5552 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL); 5553 5554 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL); 5555 5556 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5557 5558 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5559 // We also need to mark copied objects. 5560 copy_non_heap_cl = ©_mark_non_heap_cl; 5561 } 5562 5563 // Is alive closure 5564 G1AlwaysAliveClosure always_alive(_g1h); 5565 5566 // Copying keep alive closure. Applied to referent objects that need 5567 // to be copied. 5568 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss); 5569 5570 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 5571 5572 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 5573 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 5574 5575 // limit is set using max_num_q() - which was set using ParallelGCThreads. 5576 // So this must be true - but assert just in case someone decides to 5577 // change the worker ids. 5578 assert(0 <= worker_id && worker_id < limit, "sanity"); 5579 assert(!rp->discovery_is_atomic(), "check this code"); 5580 5581 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 5582 for (uint idx = worker_id; idx < limit; idx += stride) { 5583 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 5584 5585 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 5586 while (iter.has_next()) { 5587 // Since discovery is not atomic for the CM ref processor, we 5588 // can see some null referent objects. 5589 iter.load_ptrs(DEBUG_ONLY(true)); 5590 oop ref = iter.obj(); 5591 5592 // This will filter nulls. 5593 if (iter.is_referent_alive()) { 5594 iter.make_referent_alive(); 5595 } 5596 iter.move_to_next(); 5597 } 5598 } 5599 5600 // Drain the queue - which may cause stealing 5601 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator); 5602 drain_queue.do_void(); 5603 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 5604 assert(pss.queue_is_empty(), "should be"); 5605 } 5606 }; 5607 5608 // Weak Reference processing during an evacuation pause (part 1). 5609 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) { 5610 double ref_proc_start = os::elapsedTime(); 5611 5612 ReferenceProcessor* rp = _ref_processor_stw; 5613 assert(rp->discovery_enabled(), "should have been enabled"); 5614 5615 // Any reference objects, in the collection set, that were 'discovered' 5616 // by the CM ref processor should have already been copied (either by 5617 // applying the external root copy closure to the discovered lists, or 5618 // by following an RSet entry). 5619 // 5620 // But some of the referents, that are in the collection set, that these 5621 // reference objects point to may not have been copied: the STW ref 5622 // processor would have seen that the reference object had already 5623 // been 'discovered' and would have skipped discovering the reference, 5624 // but would not have treated the reference object as a regular oop. 5625 // As a result the copy closure would not have been applied to the 5626 // referent object. 5627 // 5628 // We need to explicitly copy these referent objects - the references 5629 // will be processed at the end of remarking. 5630 // 5631 // We also need to do this copying before we process the reference 5632 // objects discovered by the STW ref processor in case one of these 5633 // referents points to another object which is also referenced by an 5634 // object discovered by the STW ref processor. 5635 5636 assert(!G1CollectedHeap::use_parallel_gc_threads() || 5637 no_of_gc_workers == workers()->active_workers(), 5638 "Need to reset active GC workers"); 5639 5640 set_par_threads(no_of_gc_workers); 5641 G1ParPreserveCMReferentsTask keep_cm_referents(this, 5642 no_of_gc_workers, 5643 _task_queues); 5644 5645 if (G1CollectedHeap::use_parallel_gc_threads()) { 5646 workers()->run_task(&keep_cm_referents); 5647 } else { 5648 keep_cm_referents.work(0); 5649 } 5650 5651 set_par_threads(0); 5652 5653 // Closure to test whether a referent is alive. 5654 G1STWIsAliveClosure is_alive(this); 5655 5656 // Even when parallel reference processing is enabled, the processing 5657 // of JNI refs is serial and performed serially by the current thread 5658 // rather than by a worker. The following PSS will be used for processing 5659 // JNI refs. 5660 5661 // Use only a single queue for this PSS. 5662 G1ParScanThreadState pss(this, 0, NULL); 5663 5664 // We do not embed a reference processor in the copying/scanning 5665 // closures while we're actually processing the discovered 5666 // reference objects. 5667 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL); 5668 5669 pss.set_evac_failure_closure(&evac_failure_cl); 5670 5671 assert(pss.queue_is_empty(), "pre-condition"); 5672 5673 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL); 5674 5675 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL); 5676 5677 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5678 5679 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5680 // We also need to mark copied objects. 5681 copy_non_heap_cl = ©_mark_non_heap_cl; 5682 } 5683 5684 // Keep alive closure. 5685 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss); 5686 5687 // Serial Complete GC closure 5688 G1STWDrainQueueClosure drain_queue(this, &pss); 5689 5690 // Setup the soft refs policy... 5691 rp->setup_policy(false); 5692 5693 ReferenceProcessorStats stats; 5694 if (!rp->processing_is_mt()) { 5695 // Serial reference processing... 5696 stats = rp->process_discovered_references(&is_alive, 5697 &keep_alive, 5698 &drain_queue, 5699 NULL, 5700 _gc_timer_stw, 5701 _gc_tracer_stw->gc_id()); 5702 } else { 5703 // Parallel reference processing 5704 assert(rp->num_q() == no_of_gc_workers, "sanity"); 5705 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 5706 5707 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers); 5708 stats = rp->process_discovered_references(&is_alive, 5709 &keep_alive, 5710 &drain_queue, 5711 &par_task_executor, 5712 _gc_timer_stw, 5713 _gc_tracer_stw->gc_id()); 5714 } 5715 5716 _gc_tracer_stw->report_gc_reference_stats(stats); 5717 5718 // We have completed copying any necessary live referent objects. 5719 assert(pss.queue_is_empty(), "both queue and overflow should be empty"); 5720 5721 double ref_proc_time = os::elapsedTime() - ref_proc_start; 5722 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 5723 } 5724 5725 // Weak Reference processing during an evacuation pause (part 2). 5726 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) { 5727 double ref_enq_start = os::elapsedTime(); 5728 5729 ReferenceProcessor* rp = _ref_processor_stw; 5730 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 5731 5732 // Now enqueue any remaining on the discovered lists on to 5733 // the pending list. 5734 if (!rp->processing_is_mt()) { 5735 // Serial reference processing... 5736 rp->enqueue_discovered_references(); 5737 } else { 5738 // Parallel reference enqueueing 5739 5740 assert(no_of_gc_workers == workers()->active_workers(), 5741 "Need to reset active workers"); 5742 assert(rp->num_q() == no_of_gc_workers, "sanity"); 5743 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 5744 5745 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers); 5746 rp->enqueue_discovered_references(&par_task_executor); 5747 } 5748 5749 rp->verify_no_references_recorded(); 5750 assert(!rp->discovery_enabled(), "should have been disabled"); 5751 5752 // FIXME 5753 // CM's reference processing also cleans up the string and symbol tables. 5754 // Should we do that here also? We could, but it is a serial operation 5755 // and could significantly increase the pause time. 5756 5757 double ref_enq_time = os::elapsedTime() - ref_enq_start; 5758 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 5759 } 5760 5761 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) { 5762 _expand_heap_after_alloc_failure = true; 5763 _evacuation_failed = false; 5764 5765 // Should G1EvacuationFailureALot be in effect for this GC? 5766 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 5767 5768 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 5769 5770 // Disable the hot card cache. 5771 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 5772 hot_card_cache->reset_hot_cache_claimed_index(); 5773 hot_card_cache->set_use_cache(false); 5774 5775 const uint n_workers = workers()->active_workers(); 5776 assert(UseDynamicNumberOfGCThreads || 5777 n_workers == workers()->total_workers(), 5778 "If not dynamic should be using all the workers"); 5779 set_par_threads(n_workers); 5780 5781 init_for_evac_failure(NULL); 5782 5783 rem_set()->prepare_for_younger_refs_iterate(true); 5784 5785 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 5786 double start_par_time_sec = os::elapsedTime(); 5787 double end_par_time_sec; 5788 5789 { 5790 G1RootProcessor root_processor(this); 5791 G1ParTask g1_par_task(this, _task_queues, &root_processor); 5792 // InitialMark needs claim bits to keep track of the marked-through CLDs. 5793 if (g1_policy()->during_initial_mark_pause()) { 5794 ClassLoaderDataGraph::clear_claimed_marks(); 5795 } 5796 5797 if (G1CollectedHeap::use_parallel_gc_threads()) { 5798 // The individual threads will set their evac-failure closures. 5799 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr(); 5800 // These tasks use ShareHeap::_process_strong_tasks 5801 assert(UseDynamicNumberOfGCThreads || 5802 workers()->active_workers() == workers()->total_workers(), 5803 "If not dynamic should be using all the workers"); 5804 workers()->run_task(&g1_par_task); 5805 } else { 5806 g1_par_task.set_for_termination(n_workers); 5807 g1_par_task.work(0); 5808 } 5809 end_par_time_sec = os::elapsedTime(); 5810 5811 // Closing the inner scope will execute the destructor 5812 // for the G1RootProcessor object. We record the current 5813 // elapsed time before closing the scope so that time 5814 // taken for the destructor is NOT included in the 5815 // reported parallel time. 5816 } 5817 5818 G1GCPhaseTimes* phase_times = g1_policy()->phase_times(); 5819 5820 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 5821 phase_times->record_par_time(par_time_ms); 5822 5823 double code_root_fixup_time_ms = 5824 (os::elapsedTime() - end_par_time_sec) * 1000.0; 5825 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms); 5826 5827 set_par_threads(0); 5828 5829 // Process any discovered reference objects - we have 5830 // to do this _before_ we retire the GC alloc regions 5831 // as we may have to copy some 'reachable' referent 5832 // objects (and their reachable sub-graphs) that were 5833 // not copied during the pause. 5834 process_discovered_references(n_workers); 5835 5836 if (G1StringDedup::is_enabled()) { 5837 double fixup_start = os::elapsedTime(); 5838 5839 G1STWIsAliveClosure is_alive(this); 5840 G1KeepAliveClosure keep_alive(this); 5841 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, phase_times); 5842 5843 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 5844 phase_times->record_string_dedup_fixup_time(fixup_time_ms); 5845 } 5846 5847 _allocator->release_gc_alloc_regions(n_workers, evacuation_info); 5848 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 5849 5850 // Reset and re-enable the hot card cache. 5851 // Note the counts for the cards in the regions in the 5852 // collection set are reset when the collection set is freed. 5853 hot_card_cache->reset_hot_cache(); 5854 hot_card_cache->set_use_cache(true); 5855 5856 purge_code_root_memory(); 5857 5858 if (g1_policy()->during_initial_mark_pause()) { 5859 // Reset the claim values set during marking the strong code roots 5860 reset_heap_region_claim_values(); 5861 } 5862 5863 finalize_for_evac_failure(); 5864 5865 if (evacuation_failed()) { 5866 remove_self_forwarding_pointers(); 5867 5868 // Reset the G1EvacuationFailureALot counters and flags 5869 // Note: the values are reset only when an actual 5870 // evacuation failure occurs. 5871 NOT_PRODUCT(reset_evacuation_should_fail();) 5872 } 5873 5874 // Enqueue any remaining references remaining on the STW 5875 // reference processor's discovered lists. We need to do 5876 // this after the card table is cleaned (and verified) as 5877 // the act of enqueueing entries on to the pending list 5878 // will log these updates (and dirty their associated 5879 // cards). We need these updates logged to update any 5880 // RSets. 5881 enqueue_discovered_references(n_workers); 5882 5883 redirty_logged_cards(); 5884 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 5885 } 5886 5887 void G1CollectedHeap::free_region(HeapRegion* hr, 5888 FreeRegionList* free_list, 5889 bool par, 5890 bool locked) { 5891 assert(!hr->is_free(), "the region should not be free"); 5892 assert(!hr->is_empty(), "the region should not be empty"); 5893 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 5894 assert(free_list != NULL, "pre-condition"); 5895 5896 if (G1VerifyBitmaps) { 5897 MemRegion mr(hr->bottom(), hr->end()); 5898 concurrent_mark()->clearRangePrevBitmap(mr); 5899 } 5900 5901 // Clear the card counts for this region. 5902 // Note: we only need to do this if the region is not young 5903 // (since we don't refine cards in young regions). 5904 if (!hr->is_young()) { 5905 _cg1r->hot_card_cache()->reset_card_counts(hr); 5906 } 5907 hr->hr_clear(par, true /* clear_space */, locked /* locked */); 5908 free_list->add_ordered(hr); 5909 } 5910 5911 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 5912 FreeRegionList* free_list, 5913 bool par) { 5914 assert(hr->startsHumongous(), "this is only for starts humongous regions"); 5915 assert(free_list != NULL, "pre-condition"); 5916 5917 size_t hr_capacity = hr->capacity(); 5918 // We need to read this before we make the region non-humongous, 5919 // otherwise the information will be gone. 5920 uint last_index = hr->last_hc_index(); 5921 hr->clear_humongous(); 5922 free_region(hr, free_list, par); 5923 5924 uint i = hr->hrm_index() + 1; 5925 while (i < last_index) { 5926 HeapRegion* curr_hr = region_at(i); 5927 assert(curr_hr->continuesHumongous(), "invariant"); 5928 curr_hr->clear_humongous(); 5929 free_region(curr_hr, free_list, par); 5930 i += 1; 5931 } 5932 } 5933 5934 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, 5935 const HeapRegionSetCount& humongous_regions_removed) { 5936 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) { 5937 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 5938 _old_set.bulk_remove(old_regions_removed); 5939 _humongous_set.bulk_remove(humongous_regions_removed); 5940 } 5941 5942 } 5943 5944 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 5945 assert(list != NULL, "list can't be null"); 5946 if (!list->is_empty()) { 5947 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 5948 _hrm.insert_list_into_free_list(list); 5949 } 5950 } 5951 5952 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 5953 _allocator->decrease_used(bytes); 5954 } 5955 5956 class G1ParCleanupCTTask : public AbstractGangTask { 5957 G1SATBCardTableModRefBS* _ct_bs; 5958 G1CollectedHeap* _g1h; 5959 HeapRegion* volatile _su_head; 5960 public: 5961 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs, 5962 G1CollectedHeap* g1h) : 5963 AbstractGangTask("G1 Par Cleanup CT Task"), 5964 _ct_bs(ct_bs), _g1h(g1h) { } 5965 5966 void work(uint worker_id) { 5967 HeapRegion* r; 5968 while (r = _g1h->pop_dirty_cards_region()) { 5969 clear_cards(r); 5970 } 5971 } 5972 5973 void clear_cards(HeapRegion* r) { 5974 // Cards of the survivors should have already been dirtied. 5975 if (!r->is_survivor()) { 5976 _ct_bs->clear(MemRegion(r->bottom(), r->end())); 5977 } 5978 } 5979 }; 5980 5981 #ifndef PRODUCT 5982 class G1VerifyCardTableCleanup: public HeapRegionClosure { 5983 G1CollectedHeap* _g1h; 5984 G1SATBCardTableModRefBS* _ct_bs; 5985 public: 5986 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs) 5987 : _g1h(g1h), _ct_bs(ct_bs) { } 5988 virtual bool doHeapRegion(HeapRegion* r) { 5989 if (r->is_survivor()) { 5990 _g1h->verify_dirty_region(r); 5991 } else { 5992 _g1h->verify_not_dirty_region(r); 5993 } 5994 return false; 5995 } 5996 }; 5997 5998 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) { 5999 // All of the region should be clean. 6000 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 6001 MemRegion mr(hr->bottom(), hr->end()); 6002 ct_bs->verify_not_dirty_region(mr); 6003 } 6004 6005 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) { 6006 // We cannot guarantee that [bottom(),end()] is dirty. Threads 6007 // dirty allocated blocks as they allocate them. The thread that 6008 // retires each region and replaces it with a new one will do a 6009 // maximal allocation to fill in [pre_dummy_top(),end()] but will 6010 // not dirty that area (one less thing to have to do while holding 6011 // a lock). So we can only verify that [bottom(),pre_dummy_top()] 6012 // is dirty. 6013 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 6014 MemRegion mr(hr->bottom(), hr->pre_dummy_top()); 6015 if (hr->is_young()) { 6016 ct_bs->verify_g1_young_region(mr); 6017 } else { 6018 ct_bs->verify_dirty_region(mr); 6019 } 6020 } 6021 6022 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) { 6023 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 6024 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) { 6025 verify_dirty_region(hr); 6026 } 6027 } 6028 6029 void G1CollectedHeap::verify_dirty_young_regions() { 6030 verify_dirty_young_list(_young_list->first_region()); 6031 } 6032 6033 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap, 6034 HeapWord* tams, HeapWord* end) { 6035 guarantee(tams <= end, 6036 err_msg("tams: " PTR_FORMAT " end: " PTR_FORMAT, tams, end)); 6037 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end); 6038 if (result < end) { 6039 gclog_or_tty->cr(); 6040 gclog_or_tty->print_cr("## wrong marked address on %s bitmap: " PTR_FORMAT, 6041 bitmap_name, result); 6042 gclog_or_tty->print_cr("## %s tams: " PTR_FORMAT " end: " PTR_FORMAT, 6043 bitmap_name, tams, end); 6044 return false; 6045 } 6046 return true; 6047 } 6048 6049 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) { 6050 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap(); 6051 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap(); 6052 6053 HeapWord* bottom = hr->bottom(); 6054 HeapWord* ptams = hr->prev_top_at_mark_start(); 6055 HeapWord* ntams = hr->next_top_at_mark_start(); 6056 HeapWord* end = hr->end(); 6057 6058 bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end); 6059 6060 bool res_n = true; 6061 // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window 6062 // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap 6063 // if we happen to be in that state. 6064 if (mark_in_progress() || !_cmThread->in_progress()) { 6065 res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end); 6066 } 6067 if (!res_p || !res_n) { 6068 gclog_or_tty->print_cr("#### Bitmap verification failed for " HR_FORMAT, 6069 HR_FORMAT_PARAMS(hr)); 6070 gclog_or_tty->print_cr("#### Caller: %s", caller); 6071 return false; 6072 } 6073 return true; 6074 } 6075 6076 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) { 6077 if (!G1VerifyBitmaps) return; 6078 6079 guarantee(verify_bitmaps(caller, hr), "bitmap verification"); 6080 } 6081 6082 class G1VerifyBitmapClosure : public HeapRegionClosure { 6083 private: 6084 const char* _caller; 6085 G1CollectedHeap* _g1h; 6086 bool _failures; 6087 6088 public: 6089 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) : 6090 _caller(caller), _g1h(g1h), _failures(false) { } 6091 6092 bool failures() { return _failures; } 6093 6094 virtual bool doHeapRegion(HeapRegion* hr) { 6095 if (hr->continuesHumongous()) return false; 6096 6097 bool result = _g1h->verify_bitmaps(_caller, hr); 6098 if (!result) { 6099 _failures = true; 6100 } 6101 return false; 6102 } 6103 }; 6104 6105 void G1CollectedHeap::check_bitmaps(const char* caller) { 6106 if (!G1VerifyBitmaps) return; 6107 6108 G1VerifyBitmapClosure cl(caller, this); 6109 heap_region_iterate(&cl); 6110 guarantee(!cl.failures(), "bitmap verification"); 6111 } 6112 6113 class G1CheckCSetFastTableClosure : public HeapRegionClosure { 6114 private: 6115 bool _failures; 6116 public: 6117 G1CheckCSetFastTableClosure() : HeapRegionClosure(), _failures(false) { } 6118 6119 virtual bool doHeapRegion(HeapRegion* hr) { 6120 uint i = hr->hrm_index(); 6121 InCSetState cset_state = (InCSetState) G1CollectedHeap::heap()->_in_cset_fast_test.get_by_index(i); 6122 if (hr->isHumongous()) { 6123 if (hr->in_collection_set()) { 6124 gclog_or_tty->print_cr("\n## humongous region %u in CSet", i); 6125 _failures = true; 6126 return true; 6127 } 6128 if (cset_state.is_in_cset()) { 6129 gclog_or_tty->print_cr("\n## inconsistent cset state %d for humongous region %u", cset_state.value(), i); 6130 _failures = true; 6131 return true; 6132 } 6133 if (hr->continuesHumongous() && cset_state.is_humongous()) { 6134 gclog_or_tty->print_cr("\n## inconsistent cset state %d for continues humongous region %u", cset_state.value(), i); 6135 _failures = true; 6136 return true; 6137 } 6138 } else { 6139 if (cset_state.is_humongous()) { 6140 gclog_or_tty->print_cr("\n## inconsistent cset state %d for non-humongous region %u", cset_state.value(), i); 6141 _failures = true; 6142 return true; 6143 } 6144 if (hr->in_collection_set() != cset_state.is_in_cset()) { 6145 gclog_or_tty->print_cr("\n## in CSet %d / cset state %d inconsistency for region %u", 6146 hr->in_collection_set(), cset_state.value(), i); 6147 _failures = true; 6148 return true; 6149 } 6150 if (cset_state.is_in_cset()) { 6151 if (hr->is_young() != (cset_state.is_young())) { 6152 gclog_or_tty->print_cr("\n## is_young %d / cset state %d inconsistency for region %u", 6153 hr->is_young(), cset_state.value(), i); 6154 _failures = true; 6155 return true; 6156 } 6157 if (hr->is_old() != (cset_state.is_old())) { 6158 gclog_or_tty->print_cr("\n## is_old %d / cset state %d inconsistency for region %u", 6159 hr->is_old(), cset_state.value(), i); 6160 _failures = true; 6161 return true; 6162 } 6163 } 6164 } 6165 return false; 6166 } 6167 6168 bool failures() const { return _failures; } 6169 }; 6170 6171 bool G1CollectedHeap::check_cset_fast_test() { 6172 G1CheckCSetFastTableClosure cl; 6173 _hrm.iterate(&cl); 6174 return !cl.failures(); 6175 } 6176 #endif // PRODUCT 6177 6178 void G1CollectedHeap::cleanUpCardTable() { 6179 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 6180 double start = os::elapsedTime(); 6181 6182 { 6183 // Iterate over the dirty cards region list. 6184 G1ParCleanupCTTask cleanup_task(ct_bs, this); 6185 6186 if (G1CollectedHeap::use_parallel_gc_threads()) { 6187 set_par_threads(); 6188 workers()->run_task(&cleanup_task); 6189 set_par_threads(0); 6190 } else { 6191 while (_dirty_cards_region_list) { 6192 HeapRegion* r = _dirty_cards_region_list; 6193 cleanup_task.clear_cards(r); 6194 _dirty_cards_region_list = r->get_next_dirty_cards_region(); 6195 if (_dirty_cards_region_list == r) { 6196 // The last region. 6197 _dirty_cards_region_list = NULL; 6198 } 6199 r->set_next_dirty_cards_region(NULL); 6200 } 6201 } 6202 #ifndef PRODUCT 6203 if (G1VerifyCTCleanup || VerifyAfterGC) { 6204 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs); 6205 heap_region_iterate(&cleanup_verifier); 6206 } 6207 #endif 6208 } 6209 6210 double elapsed = os::elapsedTime() - start; 6211 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0); 6212 } 6213 6214 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) { 6215 size_t pre_used = 0; 6216 FreeRegionList local_free_list("Local List for CSet Freeing"); 6217 6218 double young_time_ms = 0.0; 6219 double non_young_time_ms = 0.0; 6220 6221 // Since the collection set is a superset of the the young list, 6222 // all we need to do to clear the young list is clear its 6223 // head and length, and unlink any young regions in the code below 6224 _young_list->clear(); 6225 6226 G1CollectorPolicy* policy = g1_policy(); 6227 6228 double start_sec = os::elapsedTime(); 6229 bool non_young = true; 6230 6231 HeapRegion* cur = cs_head; 6232 int age_bound = -1; 6233 size_t rs_lengths = 0; 6234 6235 while (cur != NULL) { 6236 assert(!is_on_master_free_list(cur), "sanity"); 6237 if (non_young) { 6238 if (cur->is_young()) { 6239 double end_sec = os::elapsedTime(); 6240 double elapsed_ms = (end_sec - start_sec) * 1000.0; 6241 non_young_time_ms += elapsed_ms; 6242 6243 start_sec = os::elapsedTime(); 6244 non_young = false; 6245 } 6246 } else { 6247 if (!cur->is_young()) { 6248 double end_sec = os::elapsedTime(); 6249 double elapsed_ms = (end_sec - start_sec) * 1000.0; 6250 young_time_ms += elapsed_ms; 6251 6252 start_sec = os::elapsedTime(); 6253 non_young = true; 6254 } 6255 } 6256 6257 rs_lengths += cur->rem_set()->occupied_locked(); 6258 6259 HeapRegion* next = cur->next_in_collection_set(); 6260 assert(cur->in_collection_set(), "bad CS"); 6261 cur->set_next_in_collection_set(NULL); 6262 cur->set_in_collection_set(false); 6263 6264 if (cur->is_young()) { 6265 int index = cur->young_index_in_cset(); 6266 assert(index != -1, "invariant"); 6267 assert((uint) index < policy->young_cset_region_length(), "invariant"); 6268 size_t words_survived = _surviving_young_words[index]; 6269 cur->record_surv_words_in_group(words_survived); 6270 6271 // At this point the we have 'popped' cur from the collection set 6272 // (linked via next_in_collection_set()) but it is still in the 6273 // young list (linked via next_young_region()). Clear the 6274 // _next_young_region field. 6275 cur->set_next_young_region(NULL); 6276 } else { 6277 int index = cur->young_index_in_cset(); 6278 assert(index == -1, "invariant"); 6279 } 6280 6281 assert( (cur->is_young() && cur->young_index_in_cset() > -1) || 6282 (!cur->is_young() && cur->young_index_in_cset() == -1), 6283 "invariant" ); 6284 6285 if (!cur->evacuation_failed()) { 6286 MemRegion used_mr = cur->used_region(); 6287 6288 // And the region is empty. 6289 assert(!used_mr.is_empty(), "Should not have empty regions in a CS."); 6290 pre_used += cur->used(); 6291 free_region(cur, &local_free_list, false /* par */, true /* locked */); 6292 } else { 6293 cur->uninstall_surv_rate_group(); 6294 if (cur->is_young()) { 6295 cur->set_young_index_in_cset(-1); 6296 } 6297 cur->set_evacuation_failed(false); 6298 // The region is now considered to be old. 6299 cur->set_old(); 6300 _old_set.add(cur); 6301 evacuation_info.increment_collectionset_used_after(cur->used()); 6302 } 6303 cur = next; 6304 } 6305 6306 evacuation_info.set_regions_freed(local_free_list.length()); 6307 policy->record_max_rs_lengths(rs_lengths); 6308 policy->cset_regions_freed(); 6309 6310 double end_sec = os::elapsedTime(); 6311 double elapsed_ms = (end_sec - start_sec) * 1000.0; 6312 6313 if (non_young) { 6314 non_young_time_ms += elapsed_ms; 6315 } else { 6316 young_time_ms += elapsed_ms; 6317 } 6318 6319 prepend_to_freelist(&local_free_list); 6320 decrement_summary_bytes(pre_used); 6321 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms); 6322 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms); 6323 } 6324 6325 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 6326 private: 6327 FreeRegionList* _free_region_list; 6328 HeapRegionSet* _proxy_set; 6329 HeapRegionSetCount _humongous_regions_removed; 6330 size_t _freed_bytes; 6331 public: 6332 6333 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 6334 _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) { 6335 } 6336 6337 virtual bool doHeapRegion(HeapRegion* r) { 6338 if (!r->startsHumongous()) { 6339 return false; 6340 } 6341 6342 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 6343 6344 oop obj = (oop)r->bottom(); 6345 CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap(); 6346 6347 // The following checks whether the humongous object is live are sufficient. 6348 // The main additional check (in addition to having a reference from the roots 6349 // or the young gen) is whether the humongous object has a remembered set entry. 6350 // 6351 // A humongous object cannot be live if there is no remembered set for it 6352 // because: 6353 // - there can be no references from within humongous starts regions referencing 6354 // the object because we never allocate other objects into them. 6355 // (I.e. there are no intra-region references that may be missed by the 6356 // remembered set) 6357 // - as soon there is a remembered set entry to the humongous starts region 6358 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 6359 // until the end of a concurrent mark. 6360 // 6361 // It is not required to check whether the object has been found dead by marking 6362 // or not, in fact it would prevent reclamation within a concurrent cycle, as 6363 // all objects allocated during that time are considered live. 6364 // SATB marking is even more conservative than the remembered set. 6365 // So if at this point in the collection there is no remembered set entry, 6366 // nobody has a reference to it. 6367 // At the start of collection we flush all refinement logs, and remembered sets 6368 // are completely up-to-date wrt to references to the humongous object. 6369 // 6370 // Other implementation considerations: 6371 // - never consider object arrays at this time because they would pose 6372 // considerable effort for cleaning up the the remembered sets. This is 6373 // required because stale remembered sets might reference locations that 6374 // are currently allocated into. 6375 uint region_idx = r->hrm_index(); 6376 if (!g1h->is_humongous_reclaim_candidate(region_idx) || 6377 !r->rem_set()->is_empty()) { 6378 6379 if (G1TraceEagerReclaimHumongousObjects) { 6380 gclog_or_tty->print_cr("Live humongous region %u size " SIZE_FORMAT " start " PTR_FORMAT " length " UINT32_FORMAT " with remset " SIZE_FORMAT " code roots " SIZE_FORMAT " is marked %d reclaim candidate %d type array %d", 6381 region_idx, 6382 obj->size()*HeapWordSize, 6383 r->bottom(), 6384 r->region_num(), 6385 r->rem_set()->occupied(), 6386 r->rem_set()->strong_code_roots_list_length(), 6387 next_bitmap->isMarked(r->bottom()), 6388 g1h->is_humongous_reclaim_candidate(region_idx), 6389 obj->is_typeArray() 6390 ); 6391 } 6392 6393 return false; 6394 } 6395 6396 guarantee(obj->is_typeArray(), 6397 err_msg("Only eagerly reclaiming type arrays is supported, but the object " 6398 PTR_FORMAT " is not.", 6399 r->bottom())); 6400 6401 if (G1TraceEagerReclaimHumongousObjects) { 6402 gclog_or_tty->print_cr("Dead humongous region %u size " SIZE_FORMAT " start " PTR_FORMAT " length " UINT32_FORMAT " with remset " SIZE_FORMAT " code roots " SIZE_FORMAT " is marked %d reclaim candidate %d type array %d", 6403 region_idx, 6404 obj->size()*HeapWordSize, 6405 r->bottom(), 6406 r->region_num(), 6407 r->rem_set()->occupied(), 6408 r->rem_set()->strong_code_roots_list_length(), 6409 next_bitmap->isMarked(r->bottom()), 6410 g1h->is_humongous_reclaim_candidate(region_idx), 6411 obj->is_typeArray() 6412 ); 6413 } 6414 // Need to clear mark bit of the humongous object if already set. 6415 if (next_bitmap->isMarked(r->bottom())) { 6416 next_bitmap->clear(r->bottom()); 6417 } 6418 _freed_bytes += r->used(); 6419 r->set_containing_set(NULL); 6420 _humongous_regions_removed.increment(1u, r->capacity()); 6421 g1h->free_humongous_region(r, _free_region_list, false); 6422 6423 return false; 6424 } 6425 6426 HeapRegionSetCount& humongous_free_count() { 6427 return _humongous_regions_removed; 6428 } 6429 6430 size_t bytes_freed() const { 6431 return _freed_bytes; 6432 } 6433 6434 size_t humongous_reclaimed() const { 6435 return _humongous_regions_removed.length(); 6436 } 6437 }; 6438 6439 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 6440 assert_at_safepoint(true); 6441 6442 if (!G1EagerReclaimHumongousObjects || 6443 (!_has_humongous_reclaim_candidates && !G1TraceEagerReclaimHumongousObjects)) { 6444 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 6445 return; 6446 } 6447 6448 double start_time = os::elapsedTime(); 6449 6450 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 6451 6452 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 6453 heap_region_iterate(&cl); 6454 6455 HeapRegionSetCount empty_set; 6456 remove_from_old_sets(empty_set, cl.humongous_free_count()); 6457 6458 G1HRPrinter* hr_printer = _g1h->hr_printer(); 6459 if (hr_printer->is_active()) { 6460 FreeRegionListIterator iter(&local_cleanup_list); 6461 while (iter.more_available()) { 6462 HeapRegion* hr = iter.get_next(); 6463 hr_printer->cleanup(hr); 6464 } 6465 } 6466 6467 prepend_to_freelist(&local_cleanup_list); 6468 decrement_summary_bytes(cl.bytes_freed()); 6469 6470 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 6471 cl.humongous_reclaimed()); 6472 } 6473 6474 // This routine is similar to the above but does not record 6475 // any policy statistics or update free lists; we are abandoning 6476 // the current incremental collection set in preparation of a 6477 // full collection. After the full GC we will start to build up 6478 // the incremental collection set again. 6479 // This is only called when we're doing a full collection 6480 // and is immediately followed by the tearing down of the young list. 6481 6482 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) { 6483 HeapRegion* cur = cs_head; 6484 6485 while (cur != NULL) { 6486 HeapRegion* next = cur->next_in_collection_set(); 6487 assert(cur->in_collection_set(), "bad CS"); 6488 cur->set_next_in_collection_set(NULL); 6489 cur->set_in_collection_set(false); 6490 cur->set_young_index_in_cset(-1); 6491 cur = next; 6492 } 6493 } 6494 6495 void G1CollectedHeap::set_free_regions_coming() { 6496 if (G1ConcRegionFreeingVerbose) { 6497 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 6498 "setting free regions coming"); 6499 } 6500 6501 assert(!free_regions_coming(), "pre-condition"); 6502 _free_regions_coming = true; 6503 } 6504 6505 void G1CollectedHeap::reset_free_regions_coming() { 6506 assert(free_regions_coming(), "pre-condition"); 6507 6508 { 6509 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6510 _free_regions_coming = false; 6511 SecondaryFreeList_lock->notify_all(); 6512 } 6513 6514 if (G1ConcRegionFreeingVerbose) { 6515 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 6516 "reset free regions coming"); 6517 } 6518 } 6519 6520 void G1CollectedHeap::wait_while_free_regions_coming() { 6521 // Most of the time we won't have to wait, so let's do a quick test 6522 // first before we take the lock. 6523 if (!free_regions_coming()) { 6524 return; 6525 } 6526 6527 if (G1ConcRegionFreeingVerbose) { 6528 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 6529 "waiting for free regions"); 6530 } 6531 6532 { 6533 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6534 while (free_regions_coming()) { 6535 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 6536 } 6537 } 6538 6539 if (G1ConcRegionFreeingVerbose) { 6540 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 6541 "done waiting for free regions"); 6542 } 6543 } 6544 6545 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 6546 assert(heap_lock_held_for_gc(), 6547 "the heap lock should already be held by or for this thread"); 6548 _young_list->push_region(hr); 6549 } 6550 6551 class NoYoungRegionsClosure: public HeapRegionClosure { 6552 private: 6553 bool _success; 6554 public: 6555 NoYoungRegionsClosure() : _success(true) { } 6556 bool doHeapRegion(HeapRegion* r) { 6557 if (r->is_young()) { 6558 gclog_or_tty->print_cr("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young", 6559 r->bottom(), r->end()); 6560 _success = false; 6561 } 6562 return false; 6563 } 6564 bool success() { return _success; } 6565 }; 6566 6567 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) { 6568 bool ret = _young_list->check_list_empty(check_sample); 6569 6570 if (check_heap) { 6571 NoYoungRegionsClosure closure; 6572 heap_region_iterate(&closure); 6573 ret = ret && closure.success(); 6574 } 6575 6576 return ret; 6577 } 6578 6579 class TearDownRegionSetsClosure : public HeapRegionClosure { 6580 private: 6581 HeapRegionSet *_old_set; 6582 6583 public: 6584 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 6585 6586 bool doHeapRegion(HeapRegion* r) { 6587 if (r->is_old()) { 6588 _old_set->remove(r); 6589 } else { 6590 // We ignore free regions, we'll empty the free list afterwards. 6591 // We ignore young regions, we'll empty the young list afterwards. 6592 // We ignore humongous regions, we're not tearing down the 6593 // humongous regions set. 6594 assert(r->is_free() || r->is_young() || r->isHumongous(), 6595 "it cannot be another type"); 6596 } 6597 return false; 6598 } 6599 6600 ~TearDownRegionSetsClosure() { 6601 assert(_old_set->is_empty(), "post-condition"); 6602 } 6603 }; 6604 6605 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 6606 assert_at_safepoint(true /* should_be_vm_thread */); 6607 6608 if (!free_list_only) { 6609 TearDownRegionSetsClosure cl(&_old_set); 6610 heap_region_iterate(&cl); 6611 6612 // Note that emptying the _young_list is postponed and instead done as 6613 // the first step when rebuilding the regions sets again. The reason for 6614 // this is that during a full GC string deduplication needs to know if 6615 // a collected region was young or old when the full GC was initiated. 6616 } 6617 _hrm.remove_all_free_regions(); 6618 } 6619 6620 class RebuildRegionSetsClosure : public HeapRegionClosure { 6621 private: 6622 bool _free_list_only; 6623 HeapRegionSet* _old_set; 6624 HeapRegionManager* _hrm; 6625 size_t _total_used; 6626 6627 public: 6628 RebuildRegionSetsClosure(bool free_list_only, 6629 HeapRegionSet* old_set, HeapRegionManager* hrm) : 6630 _free_list_only(free_list_only), 6631 _old_set(old_set), _hrm(hrm), _total_used(0) { 6632 assert(_hrm->num_free_regions() == 0, "pre-condition"); 6633 if (!free_list_only) { 6634 assert(_old_set->is_empty(), "pre-condition"); 6635 } 6636 } 6637 6638 bool doHeapRegion(HeapRegion* r) { 6639 if (r->continuesHumongous()) { 6640 return false; 6641 } 6642 6643 if (r->is_empty()) { 6644 // Add free regions to the free list 6645 r->set_free(); 6646 r->set_allocation_context(AllocationContext::system()); 6647 _hrm->insert_into_free_list(r); 6648 } else if (!_free_list_only) { 6649 assert(!r->is_young(), "we should not come across young regions"); 6650 6651 if (r->isHumongous()) { 6652 // We ignore humongous regions, we left the humongous set unchanged 6653 } else { 6654 // Objects that were compacted would have ended up on regions 6655 // that were previously old or free. 6656 assert(r->is_free() || r->is_old(), "invariant"); 6657 // We now consider them old, so register as such. 6658 r->set_old(); 6659 _old_set->add(r); 6660 } 6661 _total_used += r->used(); 6662 } 6663 6664 return false; 6665 } 6666 6667 size_t total_used() { 6668 return _total_used; 6669 } 6670 }; 6671 6672 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 6673 assert_at_safepoint(true /* should_be_vm_thread */); 6674 6675 if (!free_list_only) { 6676 _young_list->empty_list(); 6677 } 6678 6679 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 6680 heap_region_iterate(&cl); 6681 6682 if (!free_list_only) { 6683 _allocator->set_used(cl.total_used()); 6684 } 6685 assert(_allocator->used_unlocked() == recalculate_used(), 6686 err_msg("inconsistent _allocator->used_unlocked(), " 6687 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT, 6688 _allocator->used_unlocked(), recalculate_used())); 6689 } 6690 6691 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 6692 _refine_cte_cl->set_concurrent(concurrent); 6693 } 6694 6695 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 6696 HeapRegion* hr = heap_region_containing(p); 6697 return hr->is_in(p); 6698 } 6699 6700 // Methods for the mutator alloc region 6701 6702 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 6703 bool force) { 6704 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6705 assert(!force || g1_policy()->can_expand_young_list(), 6706 "if force is true we should be able to expand the young list"); 6707 bool young_list_full = g1_policy()->is_young_list_full(); 6708 if (force || !young_list_full) { 6709 HeapRegion* new_alloc_region = new_region(word_size, 6710 false /* is_old */, 6711 false /* do_expand */); 6712 if (new_alloc_region != NULL) { 6713 set_region_short_lived_locked(new_alloc_region); 6714 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full); 6715 check_bitmaps("Mutator Region Allocation", new_alloc_region); 6716 return new_alloc_region; 6717 } 6718 } 6719 return NULL; 6720 } 6721 6722 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 6723 size_t allocated_bytes) { 6724 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6725 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 6726 6727 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region); 6728 _allocator->increase_used(allocated_bytes); 6729 _hr_printer.retire(alloc_region); 6730 // We update the eden sizes here, when the region is retired, 6731 // instead of when it's allocated, since this is the point that its 6732 // used space has been recored in _summary_bytes_used. 6733 g1mm()->update_eden_size(); 6734 } 6735 6736 void G1CollectedHeap::set_par_threads() { 6737 // Don't change the number of workers. Use the value previously set 6738 // in the workgroup. 6739 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise"); 6740 uint n_workers = workers()->active_workers(); 6741 assert(UseDynamicNumberOfGCThreads || 6742 n_workers == workers()->total_workers(), 6743 "Otherwise should be using the total number of workers"); 6744 if (n_workers == 0) { 6745 assert(false, "Should have been set in prior evacuation pause."); 6746 n_workers = ParallelGCThreads; 6747 workers()->set_active_workers(n_workers); 6748 } 6749 set_par_threads(n_workers); 6750 } 6751 6752 // Methods for the GC alloc regions 6753 6754 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, 6755 uint count, 6756 InCSetState dest) { 6757 assert(FreeList_lock->owned_by_self(), "pre-condition"); 6758 6759 if (count < g1_policy()->max_regions(dest)) { 6760 const bool is_survivor = (dest.is_young()); 6761 HeapRegion* new_alloc_region = new_region(word_size, 6762 !is_survivor, 6763 true /* do_expand */); 6764 if (new_alloc_region != NULL) { 6765 // We really only need to do this for old regions given that we 6766 // should never scan survivors. But it doesn't hurt to do it 6767 // for survivors too. 6768 new_alloc_region->record_timestamp(); 6769 if (is_survivor) { 6770 new_alloc_region->set_survivor(); 6771 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor); 6772 check_bitmaps("Survivor Region Allocation", new_alloc_region); 6773 } else { 6774 new_alloc_region->set_old(); 6775 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old); 6776 check_bitmaps("Old Region Allocation", new_alloc_region); 6777 } 6778 bool during_im = g1_policy()->during_initial_mark_pause(); 6779 new_alloc_region->note_start_of_copying(during_im); 6780 return new_alloc_region; 6781 } 6782 } 6783 return NULL; 6784 } 6785 6786 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 6787 size_t allocated_bytes, 6788 InCSetState dest) { 6789 bool during_im = g1_policy()->during_initial_mark_pause(); 6790 alloc_region->note_end_of_copying(during_im); 6791 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 6792 if (dest.is_young()) { 6793 young_list()->add_survivor_region(alloc_region); 6794 } else { 6795 _old_set.add(alloc_region); 6796 } 6797 _hr_printer.retire(alloc_region); 6798 } 6799 6800 // Heap region set verification 6801 6802 class VerifyRegionListsClosure : public HeapRegionClosure { 6803 private: 6804 HeapRegionSet* _old_set; 6805 HeapRegionSet* _humongous_set; 6806 HeapRegionManager* _hrm; 6807 6808 public: 6809 HeapRegionSetCount _old_count; 6810 HeapRegionSetCount _humongous_count; 6811 HeapRegionSetCount _free_count; 6812 6813 VerifyRegionListsClosure(HeapRegionSet* old_set, 6814 HeapRegionSet* humongous_set, 6815 HeapRegionManager* hrm) : 6816 _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm), 6817 _old_count(), _humongous_count(), _free_count(){ } 6818 6819 bool doHeapRegion(HeapRegion* hr) { 6820 if (hr->continuesHumongous()) { 6821 return false; 6822 } 6823 6824 if (hr->is_young()) { 6825 // TODO 6826 } else if (hr->startsHumongous()) { 6827 assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrm_index())); 6828 _humongous_count.increment(1u, hr->capacity()); 6829 } else if (hr->is_empty()) { 6830 assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index())); 6831 _free_count.increment(1u, hr->capacity()); 6832 } else if (hr->is_old()) { 6833 assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index())); 6834 _old_count.increment(1u, hr->capacity()); 6835 } else { 6836 ShouldNotReachHere(); 6837 } 6838 return false; 6839 } 6840 6841 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) { 6842 guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length())); 6843 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6844 old_set->total_capacity_bytes(), _old_count.capacity())); 6845 6846 guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length())); 6847 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6848 humongous_set->total_capacity_bytes(), _humongous_count.capacity())); 6849 6850 guarantee(free_list->num_free_regions() == _free_count.length(), err_msg("Free list count mismatch. Expected %u, actual %u.", free_list->num_free_regions(), _free_count.length())); 6851 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6852 free_list->total_capacity_bytes(), _free_count.capacity())); 6853 } 6854 }; 6855 6856 void G1CollectedHeap::verify_region_sets() { 6857 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6858 6859 // First, check the explicit lists. 6860 _hrm.verify(); 6861 { 6862 // Given that a concurrent operation might be adding regions to 6863 // the secondary free list we have to take the lock before 6864 // verifying it. 6865 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6866 _secondary_free_list.verify_list(); 6867 } 6868 6869 // If a concurrent region freeing operation is in progress it will 6870 // be difficult to correctly attributed any free regions we come 6871 // across to the correct free list given that they might belong to 6872 // one of several (free_list, secondary_free_list, any local lists, 6873 // etc.). So, if that's the case we will skip the rest of the 6874 // verification operation. Alternatively, waiting for the concurrent 6875 // operation to complete will have a non-trivial effect on the GC's 6876 // operation (no concurrent operation will last longer than the 6877 // interval between two calls to verification) and it might hide 6878 // any issues that we would like to catch during testing. 6879 if (free_regions_coming()) { 6880 return; 6881 } 6882 6883 // Make sure we append the secondary_free_list on the free_list so 6884 // that all free regions we will come across can be safely 6885 // attributed to the free_list. 6886 append_secondary_free_list_if_not_empty_with_lock(); 6887 6888 // Finally, make sure that the region accounting in the lists is 6889 // consistent with what we see in the heap. 6890 6891 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm); 6892 heap_region_iterate(&cl); 6893 cl.verify_counts(&_old_set, &_humongous_set, &_hrm); 6894 } 6895 6896 // Optimized nmethod scanning 6897 6898 class RegisterNMethodOopClosure: public OopClosure { 6899 G1CollectedHeap* _g1h; 6900 nmethod* _nm; 6901 6902 template <class T> void do_oop_work(T* p) { 6903 T heap_oop = oopDesc::load_heap_oop(p); 6904 if (!oopDesc::is_null(heap_oop)) { 6905 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6906 HeapRegion* hr = _g1h->heap_region_containing(obj); 6907 assert(!hr->continuesHumongous(), 6908 err_msg("trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 6909 " starting at " HR_FORMAT, 6910 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()))); 6911 6912 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 6913 hr->add_strong_code_root_locked(_nm); 6914 } 6915 } 6916 6917 public: 6918 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6919 _g1h(g1h), _nm(nm) {} 6920 6921 void do_oop(oop* p) { do_oop_work(p); } 6922 void do_oop(narrowOop* p) { do_oop_work(p); } 6923 }; 6924 6925 class UnregisterNMethodOopClosure: public OopClosure { 6926 G1CollectedHeap* _g1h; 6927 nmethod* _nm; 6928 6929 template <class T> void do_oop_work(T* p) { 6930 T heap_oop = oopDesc::load_heap_oop(p); 6931 if (!oopDesc::is_null(heap_oop)) { 6932 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6933 HeapRegion* hr = _g1h->heap_region_containing(obj); 6934 assert(!hr->continuesHumongous(), 6935 err_msg("trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT 6936 " starting at " HR_FORMAT, 6937 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()))); 6938 6939 hr->remove_strong_code_root(_nm); 6940 } 6941 } 6942 6943 public: 6944 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6945 _g1h(g1h), _nm(nm) {} 6946 6947 void do_oop(oop* p) { do_oop_work(p); } 6948 void do_oop(narrowOop* p) { do_oop_work(p); } 6949 }; 6950 6951 void G1CollectedHeap::register_nmethod(nmethod* nm) { 6952 CollectedHeap::register_nmethod(nm); 6953 6954 guarantee(nm != NULL, "sanity"); 6955 RegisterNMethodOopClosure reg_cl(this, nm); 6956 nm->oops_do(®_cl); 6957 } 6958 6959 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 6960 CollectedHeap::unregister_nmethod(nm); 6961 6962 guarantee(nm != NULL, "sanity"); 6963 UnregisterNMethodOopClosure reg_cl(this, nm); 6964 nm->oops_do(®_cl, true); 6965 } 6966 6967 void G1CollectedHeap::purge_code_root_memory() { 6968 double purge_start = os::elapsedTime(); 6969 G1CodeRootSet::purge(); 6970 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 6971 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 6972 } 6973 6974 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 6975 G1CollectedHeap* _g1h; 6976 6977 public: 6978 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 6979 _g1h(g1h) {} 6980 6981 void do_code_blob(CodeBlob* cb) { 6982 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 6983 if (nm == NULL) { 6984 return; 6985 } 6986 6987 if (ScavengeRootsInCode) { 6988 _g1h->register_nmethod(nm); 6989 } 6990 } 6991 }; 6992 6993 void G1CollectedHeap::rebuild_strong_code_roots() { 6994 RebuildStrongCodeRootClosure blob_cl(this); 6995 CodeCache::blobs_do(&blob_cl); 6996 }